As recommended in a comment, I used the "Google Maps Platform API Checker" Chrome add-in to identify and resolve the issue.
Essentially, this add-in directed me to here where I was able to sign in to Google and create a free API key.
Afterwards, I updated my JavaScript and it immediately resolved this issue.
Old JavaScript: ...script src="https://maps.googleapis.com/maps/api/js?v=3" ...
Updated Javascript:...script src="https://maps.googleapis.com/maps/api/js?key=*****GOOGLE API KEY******&v=3" ...
The add-in then validated the JS API call. Hope this helps someone resolve the issue quickly!