We have created a sub theme using Seven in Drupal 9. Our task is to upgrade to Drupal 10. After installing the Seven contrib theme on the Drupal 9 version (before attempting the upgrade to 10) an HTTP error 500 page shows when clicking on Settings under Appearance for both Seven 1.0.0 and the sub theme we created. Do you have any ideas of what went wrong? Thank you in advance.
Active
1.0
User interface