Three Items

A. Unable to Enter a valid Google Maps API Key. See comments in ( ) under the 1-2-3.
1. Check if you typed the key correctly.
(yes, copied exactly from the Google Cloud Platform)
2. If you use the restriction setting on Google try to remove that, wait a few minutes for google to apply your changes and then check again if the key works here. If it does, you probably have a syntax error in your referrer url.
(removed restrictions, waited 10 minutes. nothing)
3. If none of this helps: deactivate all plugins and then check if the API works by using the button above. If thats the case then one of your plugins is interfering.
(no plugins are activated)

B. Unable to remove the circle (top-right) from the LayerSlider. I tried a handful of things, nothing worked.

C. Enfold Theme Options >Main Menu Links – Change the styling for your main menu links… .I changed the color of the links, hit update, and nothing changes.