Seasons doesn't work

I have every game downloaded and installed for Sims 4 via G4TW, including Island Living (not the newest update or stuff pack). Seasons should be installed, but in the start menu of the game, it says that it isn't istalled. Seasons didn't work before I installed Island Living either. Every other game works. 

Any idea what I could do?

If you still have Seasons releases from G4TW, extract just the "EP05" folder from it. If not, use my repack to install it (download size will be smaller).

After that run the validator (uncheck quick scan!) and post the result here.

Wow, that was easy! Thank you so much!