A bit of background might also be helpful…
1. I’ve tried to different google javascipt API keys just to be sure I didn’t set up something incorrectly. Both were responding to the requests to serve data, but nothing was displaying.
2. I followed WP Google Maps trouble shooting guide, but none of the suggestions resolved the issue. The guide is here: http://www.wpgmaps.com/documentation/troubleshooting/ I checked each of their potential issues and didn’t see anything that was causing the error. Perhaps I’ve overlooked something….?
3. All plugins are up-to-date, using the most current versions.
4. Last step was to disable one plugin at time until the maps loaded correctly – when I deactivated GP Prem the map began to display.
Hope this is helpful.