Yes, I can see English page with map, and Deutsch with no map.
BUT.
Both pages haven't direct Google Maps API loading.
Probably, this plugin stripes map API loading call.
Moreover, I have some my JavaScript and CSS files, and it stripped too.
And if it true - you can have some troubles if you enable features, for example - clusterer, managing placemarks, ajax-loading map objects and its content.
Check, for example, mine
joomla.zhuk.cc/index.php/zhgooglemap-mai...m-plugins-k2-article
You can see in page code "
maps.googleapis.com/maps/api/js?v=3&key=..."
But in yours - NO. Not any of it. I think it can caused by multilingual plugin.
Try to do little trick.
In map details, open "Advanced options".
Find field "Additional JavaScript files for loading"
and enter into it
https://maps.googleapis.com/maps/api/js?v=3&key=your_map_api_key
In this case I'll load this script, ie I defenitlely will load Map API with your key.
Do the same for your maps.
In addition to this, check, probably this plugin have ability do not stripe JS files
If it is not - your steps
- check my demo page with feature
- in page code you need to find like this "/com_zhgooglemap/assets/" all js and css calls
- in your map details css calls enter into Additional CSS files for loading
- in your map details js calls enter into Additional JavaScript files for loading