Went to download using game pass and it’s not even available for purchase, you need to redeem a code.
I can remember they mentioned a few months ago at Xbox E3 event something about a discount for current game pass owners and inclusion for the new season’s complete Xbox - PC game pass.
Same here in Australia, I have GP Ultimate. Went through Microsoft store and the xbox app and its not available at all, just greyed out with the redeem a code option.
I don’t know if it’s the actual problem. But make sure your windows is up to date (version 1903), to verify you can type winver on the research bar on windows and it will let you know your current version.
As you can see there’s 2 version on the store, and the “good” one is only available with the good update.
For me at least, that’s not the problem. I made sure it was updated when I installed the Xbox Beta app.