Topic on Extension talk:GoogleDocs4MW

Open GoogleDocs4MW.class.php with a text editor and find line 32 and 33 which shjould be

               '" src="http://spreadsheets.google.com/pub?key=' . $key .

               '&output=html&widget=true"></iframe>';

and replace it with

              '" src="https://docs.google.com/spreadsheets/d/e/' . $key .

               '/pubhtml?widget=true"></iframe>';

and save the file and the extention should now work