If your NVG / NVK displays a Illuminant error, please check the following:
First, locate the device and check the function by removing the phase in the device by removing fuse F1. The converter should now switch on and the appliance should run on battery power.
The function of the light source should then be checked and the battery voltage measured in parallel. This will give you an initial indication of the error message in the software.
Broken lamps or a weak battery always lead to this message.