allthough i thought i have made everything correct there was one site where it does not work.
I recognized that on entering the http referrers / websites on that goolge page the wildcard url/* little stars are gone by entering with return tab.
these * are very important because you want that api key for all subpages of your url.
You can insert them again by putting the cursor to that place on the url inserting the * and then click “save-button”
if these little Stars aren’t there on goole register page the api Key will only work on root url / landing page of your installation