ISSUE: TMC buttons are greyed out

Description

The TMC button for (running,) testing and submitting are not clickable and are greyed out.

Cause

The local database mapping exercises to courses is corrupted or cleared.

Solving

1. Copy all non-submitted exercises the user has started to work on to a safe place
2. Remove all affected exercises from the NetbeansProjects folder
3. Restart Netbeans
4. When prompted, download all missing exercises
5. Copy the saved exercises over the downloaded exercises