Problem:
I had received a warning email from Google saying that the API was unrestricted and the key was potentially open to abuse. So, the sensible thing to do seemed to be to restrict it to the website URL. However, this seems to be causing the problem.

How can I protect the API key without breaking the functionality of Toolset maps?
Solution:
You can add a key with restrictions (URL referrer restrictions) as the first key, and an unrestricted key as the second key. More info:
- https://toolset.com/course-lesson/creating-a-maps-api-key/#problems-with-displaying-markers-on-google-maps
- https://stackoverflow.com/questions/35288250/google-maps-javascript-api-referernotallowedmaperror

Further, here is a related ticket where one of ours user solved the issue about http referer:
- https://toolset.com/forums/topic/google-maps-api-validation-restriction-error/#post-1809879