Maybe - an interesting hint...If you zoom in - too much - the map is blended out ...It is possible that my previously described problem was simply a "zooming" problem!??! Have a great day!

I apologize, the problem was sitting in front of the keyboard....  I remembered the post from "marce1000":- To avoid browser-effects (caching, ....) , verify the issue with another browser(s). Clear browser cache, one more time.And I am happy again.....

PI 3.8.1 Update 01 fixes this Bug "CSCvw84325 - Prime Infrastructure may not render the background street maps in selected screens"....according to release notesBUT IT DOES NOT FIX THE PROBLEM...for my installation??!!??

Dear All,We also have the same issue with 3.8. (after Upgrade from 3.5). Same message...performed same actions as "18522Hannover". Stay healthy!