Firstly, Sorry for causing trouble on playing the game.
If you failed to Device sync, on your device, go to [Device settings]-[Manage Application]-[Black Survival]-[Delete data], restart the game and sign in to Black Survival.
If it doesn't work, just leave one Google account to sign in with and delete the rest for awhile and try to sign in into Black Survival.(Your account isn't actually deleted)
To delete accounts from your device, [Device settings]-[Accounts]-[Google] and select the account you could not sign in with - delete it. Restart your device, if you can properly sign into Black Survival, add the accounts you removed!
If none of the following solves the issue, if you could somehow sign in, go to [Main Lobby]-[Settings]-[Inquiry/Report] and send us an inquiry or contact us at firstname.lastname@example.org and we will look for solutions as soon as possible.