HI,
All seems fine. 

This time a new VM, with Centos 7, PHP from Remi's PHP 8.0 RPM repository for Enterprise Linux 7
Enable plugin, setup exactly same problem. You wrote: check your error logs for any related errors.
So from osticket -> Dashboard -> System logs I just see OsTicket installed, from httpd error_log and ssl_error_log no errors. How can I get more information? I also have Default Log Level: set to debug. nmap from old and new server to the Active Directory Server gives identical results.