My map is gray and there are no entry markers

The problem here is that your entries haven't been Geolocated yet, so you must now go to Google's Developer Console > Credentials > On the right side, look for the list of your API keys. 

Click on your API:



Once inside, you'll see this page:



Then, click on API restrictions, and follow these two steps below:



It should look like this:



After doing this, go back to each one of your form entries, they should appear with this message:



Click on "Geocode This Address":



That should make the entry shows up on the map.