Remote Keyboard suddenly stopped working

Hi,

I've got a MELE F10 remote control.

https://www.amazon.de/Epsilon-MeLE-F10-Deluxe-GHz/dp/B00QRRIRD2

It suddenly stopped working. I tried different USB ports for the receiver and tried different model of the remote. Nothing.

I tried a stock USB keyboard, which worked fine.

Both controls work fine on my PC.

any idea where to look?

It's libreelec 11.0.6 on raspberry 4

thanks

JPT

Correction:

the other model works. odd.