Gamekit iMessage only game?

Hi,

does anyone know if it is possible to use leaderboards in an imessage only game?

I have created leaderboards and they are live with my app. But nevertheless on authentication I always get:

[Error] _authenticateUsingAlert:Failed to authenticate player with existing credentials.Error: Error Domain=GKErrorDomain Code=15 "Der angeforderte Vorgang konnte nicht abgeschlossen werden, da die App vom Game Center nicht erkannt wird." UserInfo={GKServerStatusCode=5019, NSLocalizedDescription=Der angeforderte Vorgang konnte nicht abgeschlossen werden, da die App vom Game Center nicht erkannt wird., NSUnderlyingError=0x283d36d60 {Error Domain=GKServerErrorDomain Code=5019 "status = 5019, no game matching descriptor: ios:net.mygame.MessagesExtension:1.3:1+-1" UserInfo={GKServerStatusCode=5019, NSLocalizedFailureReason=status = 5019, no game matching descriptor: ios:net.mygame.MessagesExtension:1.3:1+-1}}}

Is it possible that iMessage only games are not supported by GameKit? As the iMessage App has the Bundle identifier net.mygame.MessagesExtension

and it seems the Leaderboard associated with it in the appastoreconnect interface is registered to net.mygame?

Or is there something I overlooked?

Thanks, Jan