Did you use the install script?
If so, Apache2 is used for ITflow. I also changed the default ports (because I'm using a reverse proxy on the same server), in the Apache config file at /etc/apache2/sites-enabled.
This is my file:
<VirtualHost *:4443>
ServerAdmin webmaster@localhost
ServerName your.itflow.com
DocumentRoot /var/www/your.itflow.com
SSLEngine on
SSLCertificateFile /etc/ssl/av-certs/certificate.crt
SSLCertificateKeyFile /etc/ssl/av-certs/certificate.key
ErrorLog ${APACHE_LOG_DIR}/error.log
CustomLog ${APACHE_LOG_DIR}/access.log combined
</VirtualHost>
<VirtualHost *:8080>
ServerAdmin webmaster@localhost
ServerName your.itflow.com
DocumentRoot /var/www/your.itflow.com
ErrorLog ${APACHE_LOG_DIR}/error.log
CustomLog ${APACHE_LOG_DIR}/access.log combined
RewriteEngine on
RewriteCond %{HTTPS} !=on
RewriteRule ^/?(.*) https://%{SERVER_NAME}/$1 [R=301,L]
</VirtualHost>
After that restart Apache: sudo systemctl restart apache2.service
I hope this helps