Just wanted to pass this on in case it can save someone a bunch of grief.
I set up a google maps API Key today and no matter what I did I could not do a proximity or location search with the Geocoder plugin.
Google insisted that my account and project were set up correctly, and I'd done this a few years ago and was following my install notes, so I believed them.
After some tearing of hair, we discovered that the Geocoding API is now located in their library of addons and must be enabled separately if you're doing proximity or location searches.
This link might get you to their library. https://console.cloud.google.com/apis/library/geocoding-backend.googleapis.com
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