Some time ago I created an example project (lets call it "example project") with Oauth2 client id for android application in Google APIs console. I also added SHA1 fingerprint and package name (for example com.package.name).
My mistake was that an application with same package name already existed. Now I need to create an Oauth2 client id for android application in the "valid project" with package name com.package.name and with SHA1 fingerprint which I added before. Obviously when I tried to add this fingerprint I got an error.
The signing fingerprint you specified is already used by another Android OAuth2 client.
After that I remembered about "example project" and deleted client id from this project. The problem is that I still not able to add this fingerprint for package name com.package.name. Client id is deleted but still I have the same error as above.
So do I have a possibility to use this fingerprint for the same package name in another project?
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 to completely remove it.
Another option is to delete the debug.keystore and generate a new one with:
keytool -genkey -v -keystore debug.keystore -alias androiddebugkey
-storepass android -keypass android -keyalg RSA -validity 14000
Remember you have to uninstall the app otherwise you get the [INSTALL_FAILED_UPDATE_INCOMPATIBLE] error.