Close the Xbox app (not minimised in taskbar)
Open up the Powershell in Admin mode and type in the three lines:
Get-AppxPackage *gamingservices* -allusers | remove-appxpackage -allusers <Enter>
Remove-Item -Path "HKLM:\System\CurrentControlSet\Services\GamingServices" -recurse <Enter>
Remove-Item -Path "HKLM:\System\CurrentControlSet\Services\GamingServicesNet" -recurse <Enter>
You may find it can't find one of the registry paths, it doesn't matter.
Reboot pc. This does actually make the difference if it works or not.
You will need to reinstall the gaming services. You can install via the xbox app but found better results via the powershell:
start ms-windows-store://pdp/?productid=9MWPM2CQNLHN
Now no more msgs in the xbox app. Game Pass games now work. Yay!
Until the next Gaming Services update where you will have to do the above procedure again.