Markers dont show up

The markers don’t show up.
In the source code the section after this comment
// Add the markers and polylines

is blank.
I deactivated and activated the plugin, no result. I checked whether the markers are installed (uploads/markers), everything looks fine.

The site is in maintainace mode, could this cause an issue?

Any ideas?

https://wordpress.org/plugins/wp-geo/