After migrating from Joomla 3 to Joomla 4, I am now receiving an error message when logging into the administrator backend.
An error has occurred.
0 Class 'JRequest' not found
When on Joomla 3 I used the Royality template with great success. After migration to Joomla 4 the Royalty stopped workin (only a white page, no errors). Then I installed the Milano. There where no errors during installation or during the J3J4 migration.