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Question

I am trying to make simple game with Google Play Games Services, but I failed to sign in to Google Play Games.

I get this error:

Answer 1

For me its that my project SHA1 is not the same as what is in the API console.
1. I've checked mine through this.
2. Went to https://console.developers.google.com and into the "Credentials" page of my project.
3. Clicked on the edit button (the pencil icon) and pasted over the SHA1
4. Worked within <2 minutes