Sudden Error: “It looks like you are trying to reinstall your Nextcloud. However the file CAN_INSTALL is missing from your config directory. Please create the file CAN_INSTALL in your config folder to continue.”

Nextcloud version 24.01
Operating system and version Ubuntu 18.4
Apache or nginx version Apache/2.4.29
PHP version 7.4

The issue you are facing:

Is this the first time you’ve seen this error? (Y/N): Y

Suddenlty my nextcould installation is not working anymore, I have not changed anything, and I’m not trying to (re)-install nextcould.

The output of your Nextcloud log in Admin > Logging:

It looks like you are trying to reinstall your Nextcloud. However the file CAN_INSTALL is missing from your config directory. Please create the file CAN_INSTALL in your config folder to continue.

The output of your config.php file in /path/to/nextcloud (make sure you remove any identifiable information!):

<?php
$CONFIG = array (
  'instanceid' => 'RANDOMSYMBOLS',
);```

I am well aware that this error was already discussed here Sudden Error: "It looks like you are trying to reinstall your Nextcloud. However the file CAN_INSTALL is missing from your config directory. Please create the file CAN_INSTALL in your config folder to continue."

However I replaced the config.php with a backup. Now I am just getting the message internal server error. Does someone have some advise for me?