Hi @world_editor Thanks for your report

From our FAQ section:

I want to add a missing season to a TV entry, but there is no "Add New Season" button!

The "Ended" and "Cancelled" TV Show Status now automatically disabled the "Add New Season" button. New seasons can't be created when a TV entry is set to Ended or Cancelled.

For ongoing series, fixing the TV show status will also bring back the ability to create a new season.

For ended/cancelled series with a missing season, you are allowed to temporarily change the TV Show Status back to "Returning Series". Just don't forget to set it back to Ended/Cancelled when you are done adding the missing content.