Google Maps is not loaded correctly

Yesss but only in frontend in the backend is not visible

I display map in site part and in admin panel the same way. The code to display the same.
I think you probably did some restriction by web server configuration. I can't explain why you get different behavior of map.

Yes is curious because is the same key for both, is not a big problem but I'm curious to know.
Do you know what setup of server can be?
I've a VM and into it I've a lot web sites with your component and only in one I've this problem. Only it has the key the others are developed before need it.

Probably you enter some wrong configuration for site (some rewrite options, or protection admin area).

For example, create new one by default settings. Or compare config file for working site and yours.