No signal while charging Nighthawk M5

I bought the M5 5G Mobile Router MR5200 a few weeks ago.

The router works very well in battery mode. However, when I connect the router to the power device (in Germany) to charge the battery, the router no longer works and I can no longer receive any signal.

So the router works only in battery mode, but not when it is connected to the mains.

Does anyone know this problem and can help me?

Thanks a lot, Klaus