I think I found the cause, but no idea how to fix it. I rechecked the error.log in apache2 and this is what I see now:
[Sat Jul 13 00:00:01.269484 2024] [mpm_prefork:notice] [pid 694] AH00163: Apache/2.4.59 (Debian) OpenSSL/3.0.11 configured -- resuming normal operations
[Sat Jul 13 00:00:01.269504 2024] [core:notice] [pid 694] AH00094: Command line: '/usr/sbin/apache2'
[Sat Jul 13 00:03:41.519670 2024] [php:warn] [pid 6586] [client 206.168.34.114:53388] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71
[Sat Jul 13 00:38:43.174178 2024] [php:warn] [pid 6585] [client 118.107.220.50:50875] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71
[Sat Jul 13 00:38:44.978525 2024] [php:warn] [pid 6587] [client 23.191.80.8:48459] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71
[Sat Jul 13 00:45:26.674540 2024] [php:warn] [pid 6585] [client 185.245.84.37:43229] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71, referer: https://suppor>
[Sat Jul 13 00:45:27.292814 2024] [php:warn] [pid 6587] [client 149.88.98.69:51047] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71, referer: https://support>
[Sat Jul 13 00:45:29.560494 2024] [php:warn] [pid 6583] [client 167.88.60.235:44839] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71, referer: https://suppor>
[Sat Jul 13 00:49:24.535277 2024] [php:warn] [pid 6587] [client 147.185.132.94:59508] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71
[Sat Jul 13 01:15:20.062138 2024] [php:warn] [pid 6584] [client 205.210.31.86:64928] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71, referer: http://206.75.>
[Sat Jul 13 01:18:57.024278 2024] [php:warn] [pid 6585] [client 71.19.252.155:37723] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71, referer: https://suppor>
[Sat Jul 13 01:18:57.497493 2024] [php:warn] [pid 6587] [client 191.96.36.135:38785] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71, referer: https://suppor>
[Sat Jul 13 01:18:59.514099 2024] [php:warn] [pid 6583] [client 179.61.228.6:56969] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71, referer: https://support>
[Sat Jul 13 01:19:00.339988 2024] [php:warn] [pid 6632] [client 172.241.250.177:43347] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71, referer: https://supp>
[Sat Jul 13 01:31:17.151958 2024] [php:warn] [pid 6583] [client 191.96.36.135:46185] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71, referer: https://suppor>
[Sat Jul 13 01:54:28.325130 2024] [core:error] [pid 8431] [client 4.240.76.242:58864] AH10244: invalid URI path (/cgi-bin/.%2e/.%2e/.%2e/.%2e/.%2e/.%2e/.%2e/.%2e/.%2e/.%2e/bin/sh)
[Sat Jul 13 01:54:29.811353 2024] [core:error] [pid 8432] [client 4.240.76.242:58874] AH10244: invalid URI path (/cgi-bin/%%32%65%%32%65/%%32%65%%32%65/%%32%65%%32%65/%%32%65%%32%65/%%32%65%%32%65/%%32%65%%32%65/%%32%65%%32%65/bin/sh)
[Sat Jul 13 02:06:46.559766 2024] [php:warn] [pid 6586] [client 47.242.224.70:57268] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71, referer: https://suppor>
[Sat Jul 13 02:12:07.572790 2024] [core:error] [pid 6587] [client 57.155.64.190:54832] AH10244: invalid URI path (/cgi-bin/.%2e/.%2e/.%2e/.%2e/.%2e/.%2e/.%2e/.%2e/.%2e/.%2e/bin/sh)
[Sat Jul 13 02:12:08.926930 2024] [core:error] [pid 8431] [client 57.155.64.190:52988] AH10244: invalid URI path (/cgi-bin/%%32%65%%32%65/%%32%65%%32%65/%%32%65%%32%65/%%32%65%%32%65/%%32%65%%32%65/%%32%65%%32%65/%%32%65%%32%65/bin/sh)
[Sat Jul 13 02:35:09.761819 2024] [php:warn] [pid 6583] [client 147.185.133.4:61780] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71, referer: http://206.75.>
[Sat Jul 13 02:46:47.935407 2024] [core:error] [pid 6586] [client 8.220.202.139:52888] AH10244: invalid URI path (/cgi-bin/.%2e/.%2e/.%2e/.%2e/.%2e/.%2e/.%2e/.%2e/.%2e/.%2e/bin/sh)
[Sat Jul 13 02:46:48.773357 2024] [core:error] [pid 6584] [client 8.220.202.139:40458] AH10244: invalid URI path (/cgi-bin/%%32%65%%32%65/%%32%65%%32%65/%%32%65%%32%65/%%32%65%%32%65/%%32%65%%32%65/%%32%65%%32%65/%%32%65%%32%65/bin/sh)
[Sat Jul 13 03:59:19.583501 2024] [php:warn] [pid 6584] [client 212.102.57.167:57405] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71, referer: https://suppo>
[Sat Jul 13 03:59:39.874745 2024] [php:warn] [pid 7748] [client 212.102.57.167:59383] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71, referer: https://suppo>
[Sat Jul 13 04:00:14.895465 2024] [php:warn] [pid 8339] [client 179.61.197.168:42695] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71, referer: https://suppo>
[Sat Jul 13 04:00:35.023557 2024] [php:warn] [pid 8431] [client 179.61.197.168:47523] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71, referer: https://suppo>
[Sat Jul 13 04:01:08.829389 2024] [php:warn] [pid 6587] [client 37.120.213.169:54859] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71, referer: https://suppo>
[Sat Jul 13 04:01:30.079253 2024] [php:warn] [pid 6584] [client 37.120.213.169:34053] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71, referer: https://suppo>
[Sat Jul 13 04:02:19.925140 2024] [php:warn] [pid 6586] [client 167.94.145.102:40658] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71
[Sat Jul 13 05:43:35.828921 2024] [php:warn] [pid 10868] [client 184.105.247.195:31110] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71, referer: https://206>
[Sat Jul 13 06:16:55.910300 2024] [php:warn] [pid 6632] [client 35.203.211.241:59316] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71
[Sat Jul 13 06:18:33.593943 2024] [php:warn] [pid 8431] [client 184.105.247.195:45416] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71, referer: http://206.7>
[Sat Jul 13 06:54:41.462686 2024] [php:warn] [pid 6587] [client 198.235.24.18:63416] PHP Warning: Undefined array key "HTTP_USER_AGENT" in /var/www/support.bossknowledge.com/login.php on line 29
[Sat Jul 13 06:54:41.469340 2024] [php:warn] [pid 6587] [client 198.235.24.18:63416] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71
[Sat Jul 13 06:56:28.784884 2024] [php:warn] [pid 6632] [client 171.244.43.14:52270] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71
[Sat Jul 13 07:14:05.690385 2024] [php:warn] [pid 8431] [client 95.217.18.177:54950] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71, referer: https://suppor>
[Sat Jul 13 07:35:45.224525 2024] [php:warn] [pid 7748] [client 167.94.145.108:57326] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71
[Sat Jul 13 07:52:26.087980 2024] [php:warn] [pid 10891] [client 83.97.73.245:40872] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71, referer: https://206.75>
[Sat Jul 13 08:15:25.390822 2024] [php:warn] [pid 10868] [client 109.71.253.194:44356] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71, referer: http://examp>
[Sat Jul 13 08:15:26.454943 2024] [php:warn] [pid 6586] [client 109.71.253.194:44384] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71, referer: http://exampl>
[Sat Jul 13 08:22:38.827940 2024] [php:warn] [pid 6587] [client 104.236.72.33:27258] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71, referer: https://206.75>
[Sat Jul 13 08:52:56.959075 2024] [php:warn] [pid 10868] [client 165.232.125.178:16646] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71, referer: http://206.>
[Sat Jul 13 09:48:42.005254 2024] [php:warn] [pid 8431] [client 167.94.138.43:54322] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71
[Sat Jul 13 10:09:16.350975 2024] [php:warn] [pid 10868] [client 24.109.104.106:54926] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71, referer: https://supp>
[Sat Jul 13 10:09:16.403896 2024] [php:error] [pid 10868] [client 24.109.104.106:54926] PHP Fatal error: Uncaught mysqli_sql_exception: Unknown column 'email_cal_str' in 'field list' in /var/www/support.bossknowledge.com/functions.php:>
[Sat Jul 13 10:09:18.994028 2024] [php:warn] [pid 6632] [client 24.109.104.106:54925] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71
[Sat Jul 13 10:09:21.362911 2024] [php:warn] [pid 6632] [client 24.109.104.106:54925] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71, referer: https://suppo>
[Sat Jul 13 10:09:21.434468 2024] [php:error] [pid 6632] [client 24.109.104.106:54925] PHP Fatal error: Uncaught mysqli_sql_exception: Unknown column 'email_cal_str' in 'field list' in /var/www/support.bossknowledge.com/functions.php:1>
[Sat Jul 13 10:12:50.548014 2024] [php:warn] [pid 8433] [client 24.109.104.106:55118] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71, referer: https://suppo>
[Sat Jul 13 10:12:50.601291 2024] [php:error] [pid 8433] [client 24.109.104.106:55118] PHP Fatal error: Uncaught mysqli_sql_exception: Unknown column 'email_cal_str' in 'field list' in /var/www/support.bossknowledge.com/functions.php:1>
[Sat Jul 13 10:13:27.565545 2024] [php:warn] [pid 8339] [client 24.109.104.106:55172] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71
[Sat Jul 13 10:13:29.531469 2024] [php:warn] [pid 8339] [client 24.109.104.106:55172] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71
[Sat Jul 13 10:13:30.582122 2024] [php:warn] [pid 8339] [client 24.109.104.106:55172] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71, referer: https://suppo>
[Sat Jul 13 10:13:30.635439 2024] [php:error] [pid 8339] [client 24.109.104.106:55172] PHP Fatal error: Uncaught mysqli_sql_exception: Unknown column 'email_cal_str' in 'field list' in /var/www/support.bossknowledge.com/functions.php:1>
[Sat Jul 13 10:17:03.860720 2024] [php:warn] [pid 10868] [client 47.88.94.28:36025] PHP Warning: Undefined array key "config_login_remember_me_expire" in /var/www/support.bossknowledge.com/login.php on line 71, referer: https://support>