Hi there,
That is strange. Actually, there is no error on my browser console regarding the API Key problem. API seems to be ok.
The problem is that usually Google Map uses iFrame to show the map. I see no iFrame on your front end code! Is it possible that you create a new page with the Classic Google Map element and add the API key and the marker destination and then kindly get back to us with the URL/User/Pass of your WordPress dashboard using the Secure Note functionality of the post to follow up the case?
Also, we will be grateful if you ask your hosting service provider that if they block iFrames in their settings or not.
Thank you.