Same problem here, I can manually generate a map on a post by entering the address. Those requests get a success in the Google API.
When generating the map using Custom Fields is when then error occurs.
So I’m wondering if the request is not being formed correctly when sending using custom field data.
As per shootraw, was working fine for several months, then stopped working.
I checked the above suggestions, I was all clear.
Anything else you can think of that I should check?