So what i can say you is what i can try to guess that it's going wrong.

I think that you are configuring an IP based restrictions in the API key for the Google app as visible in the attached image.
If i'm right, why just don't leave that field empty to have it working?
Also i'm not sure if you are aware that this field should contain the IP address of your server, in the case you want to apply a per-Ip restriction to the Google app usage.
By the way Googling about this argument you find a lot of discussions.