I had the same issue as well, below is the fix. For me, Firefox was blocking the map because it was coming over HTTP and everything else was HTTPS. If you clicked "Disable Protection on This Page" it would show the map but you had to do it every time you went to the dashboard which was really annoying. Internet Explorer was similar.
You will need to edit two files to be able to access the Google Maps API over SSL(HTTPS).
First, make a backup of ZENHOME/Products/ZenWidgets/skins/zenui/locationGeoMap.pt and, in the same directory, simpleLocationGeoMap.pt.
Edit locationGeoMap.pt and change line 15 from: (without quotes)
"src string:http://maps.googleapis.com/maps/api/js?key=${apikey}&sensor=false;"
to
"src string:https://maps-api-ssl.google.com/maps/api/js?key=${apikey}&sensor=false;"
Edit simpleLocationGeoMap.pt and change line 23 from: (without quotes)
"src string:http://maps.googleapis.com/maps/api/js?key=${apikey}&sensor=false"></script>"
to
"src string:https://maps-api-ssl.google.com/maps/api/js?key=${apikey}&sensor=false"></script>"
Then restart zopectl. You should be good to go.
Since we are talking about maps, you can also edit geomap.js under ZENHOME/Products/ZenWidgets/skins/zenui/javascript/ and set "mapTypeControl" to true(Currently line 100). This will give you a small drop down box on the map where you can toggle between a few different map views (Satellite, etc.).
Let me know if you have any issues.