WHMCS on Ubuntu 22.04 and Apache | Blank Page after installation

[NinerAlpha]

Hello all,

I spent 2 days trying to figure out what is wrong my my WHMCS and why every time I install it I get blank page for admin area. I did 3 fresh installs on my VPS and every time I get same results, installation runs fine and once that is done and I want to go to admin area I get blank page with: admin/login.php?redirect=%2Fadmin%2F url. If I set $display_errors = 'true' in configuration.php file I get Oops! page.

Apache2 error logs do not show anything, there are no errors listed under Oops! message and I have no idea what could cause this behavior. I opened ticket but got no useful information from support so maybe someone will have some troubleshooting tips for me. 

I am not professional apaceh2 handler so I would like to ask anyone replying to this with some advices to have understanding and explain it a bit so I could understand what is going on. 

Thanks everyone in advance.

[SimpleSonic]

What PHP version are you using?

Have you checked that you have all the necessary system requirements for installation?: https://docs.whmcs.com/System_Requirements

Have you checked that you are using the correct folder/file permissions? (755/644 is common for most setups)

Have you tried renaming your .htaccess file to rule out any unsupported or incorrect entries?

[NinerAlpha]

My php version is set to 8.1 and all requirements are met. I switched to nginx and it works just fine with same dependenices installed, which leads me to thing I messed up something in virtualhost configuration for Apache.