Why do I always get this error when enabling Push Notifications? I have 2 accounts, one is paid (company account) and the other one is free (personal) but both of them have the same error with no details as to why I got this error. Is this something that you can fix on your side?
Please verify that you've followed these instructions to obtain a GCM API key:
Also, there's a command to test the validity of your key. See the "Checking the validity of an API key" section on this page: