The signing fingerprint you specified is already used by another Android OAuth2 client
This error occurs when there is an existing SIGNING CERTIFICATE FINGERPRINT (SHA1) on Google Developers linked to a different account. Solution is to delete the project that is using that SHA1 in console.developers.google.com for the old/incorrect project. You cannot change the SHA1 fingerprint once it is set. Remember that deleting the project takes 7 days … Read more