Game "does not support leaderboards” error

I'm attempting to integrate a macOS game with Apple's GameKit SDK using Objective-C. So far I have been able to authenticate the user and load/update achievements, but I have had no success with leaderboards.

When attempting a

loadLeaderboardsWithCompletionHandler

Error Domain=GKErrorDomain Code=3 "The requested operation could not be completed due to an error communicating with the server." UserInfo={GKServerStatusCode=5043, NSLocalizedDescription=The requested operation could not be completed due to an error communicating with the server., NSUnderlyingError=0x600000158960 {Error Domain=GKServerErrorDomain Code=5043 "status = 5043, MyGame does not support leaderboards" UserInfo={GKServerStatusCode=5043, NSLocalizedFailureReason=status = 5043, MyGame does not support leaderboards}}}

I'm having trouble understanding why Apple's endpoint says my game does not support leaderboards. So far I have:

1. Enabled GameCenter for our app identifier
2. Enabled GameCenter on our app's App Store Connect page (currently in "prepare for submission" state)
3. I've added a leaderboard to our app group via the Features menu in App Store Connect and imported it onto the macOS App Store page

But still nothing. Any ideas?