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.