Chances are, you’ve already tried everything to get Game Center authentication working, so I’ll jump to the solution and back up to explain how I got there. Quick note: If you won’t be able to test Game Center in the Unity editor, you’ll have to test on device (or possibly with a simulator).
Authentication not working? Make a nickname
If you’ve tried everything and Game Center authentication still isn’t working, double check that your Game Center profile is up to date. I double and triple checked everything only to find that authentication was failing, because I hadn’t set a nickname on my Game Center profile. Go to Settings -> Game Center, double check all the settings, and make sure you have a Game Center profile set-up.
Full process to Support Game Center
1. Confirm you have Game Center enabled for your App Id
2. Check everything is working in Xcode. Go to Target -> Capabilities -> Game Center and set it to ‘On’. Any set-up problems will show up there.
Note: If you get an error with “Add Game Center feature to your App ID.” Try enabling Push Notifications then turning them back off again. That may be due to a bug in Xcode.
All in all, the Game Center implementation process is fairly simple if you know the pitfalls to avoid.
I hope you found this article helpful. If you have any extra issues or tips, leave them in the comments and I’ll check them out.