Hi Andy,

Joomla Admin login is managed by Joomla itself. Probably during update, not all files were overrided or are missing or problem with configuration.php file.

For Joomla problems visit: forum.joomla.org

My Free tips:

1. Take Joomla Update package and using FTP upload & override all files.
2. If you also set PHP 8.5, switch back to PHP 8.3 or PHP 8.4
3. About error messages on front-end: It means your configuration.php file is missing a line that the system expects to see—specifically, the one defining whether Debug Mode is on or off. Check if public $debug = '0'; line exists, if not - add it or correct value. The same problem is for Error Reporting line.

Problem is with Joomla file(s) after CMS migration/update, not SPPB or Helix template itself (!) And it's very easy to prove it, so it's beyond JoomShaper support.