The app worked until a few weeks ago. GrapheneOS does not miss any functionality (nor security) for the app to work. The only change is that they started blocking non-GMS Android through the thoroughly anti-competitive Play Integrity.

Hypothetically, if GrapheneOS wanted to become a certified Android, it would probably not be blocked on technical reasons, only that becoming certified (last time a contract was leaked) requires running privileged Google Play Services (which is less secure) and pre-installing a bunch of Google apps that should not be uninstallable.

How is that not anti-competitive?