Php when visiting subdomain/installer gives 404 error

Your software
My PHP version is : 7.4.2
My MariaDB version is (delete as applicable): 10.3.31

Updating/Installing Errors
I am : Installing
Upgrading/installing via / Command Line

These errors are showing in the installer :

(subdomain).mydomain.com/index.php/installer gives 404 error

These errors are showing in the Mautic log :

No Errors showing/no log files

These errors are showing in the upgrade_log.txt file (located in the root of your Mautic instance when an upgrade has been attempted - ensure you remove or redact any sensitive data such as domain names in the file path) :

No errors showing/no log files
Your problem
My problem is : When I visit mautic.mydomain.com I get a resolve()); on the screen, but nothing else, and the installer is showing a 404. Verified www-data has all permissions. New to linux/DigitalOcean, but files are all there, and my SuiteCRM is running on the same server. Any ideas where to start?

Steps I have tried to fix the problem :