Logic not updating...

I'm trying to update from my Logic Pro 10.4.1 to 10.5.1 on my Macbook Pro (mojave). When I go to the App Store and click "updates" I see only one update listed - Logic Pro X with an "update" button beside it. When I click the button it spins the little arrow for about 10 sec then stops and nothing seems to have changed ... no progress bar or anything. The little blue "update" button remains.

I don't see anything in App folder or downloads etc.

Am I missing something?

Help appreciated!