How to add Custom Markers for Gmap Module Drupal
Here is how it looks:
Request for invalid marker set notification
And here is how map field looks:
Map with a missing marker (s)
The default map is displayed.
Luckily there is a simple solution - delete gmap.markers.js file from files/js folder, and markers will regenerate by themselves.
sudo rm -rf gmap_markers.js
Now, run clear cache and all markers should be back
Marker cache cleared