Google Maps error: Oops! Something went wrong. This page didn't load Google Maps correctly

Question

First time asking on stackoverflow, so be patient if I break some rule, tried my best to solve by myself searching for a solution, but had no luck.

I used a tool to

Answer 1

Quick F12 to developer console and reload gives:

MissingKeyMapError and points to https://developers.google.com/maps/documentation/javascript/error-messages for reference.