After creating a WMS (1.3.0) in GeoServer (2.15.1) I cannot load the WMS service in Mapbender (v. 3.0.8.1). Original WMS-URL:

http://localhost:8082/geoserver/ows?service=WMS&version=1.3.0&request=GetCapabilities  

In GeoServer all of the layers are displayed correctly. The WMS layers can also be loaded properly in QGIS (WMS layer). For the app configuration I have followed the instructions from the Mapbender documentation. Independently on the chosen source in the layersets of the app the WMS cannot be loaded. I also get the errors: "element: a target element is not defined" although I have defined those elements:

I also tried to choose other sources which are already available from the source list in Mapbender but got the same errors. I am running both GeoServer and Mapbender on the OsGeoLive13 virtual machine (virtual box).

Can someone tell me why the WMS layers cannot be loaded or why do I see just an empty screen?

I simply cannot load any WMS layer in Mapbender but have followed all steps in Mapbender documentation. A problem with the GetCapabilities document could be the clue.