Decrypt o2 Homebox 6441 router?

I have a notebook Medion Akoya S6446; Win10. It can't be connected to the o2 Homebox 6441 modem despite entering the network key in the WLAN menu. Modem itself is intact because the connection to my other Acer notebook is available. What could be the problem? Medion informed me that the modem had to be decrypted, I don't quite understand? So, how?

I would delete the WLAN profile in Windows 10 and then connect the laptop freshly to your WLAN.

Here (bottom of the page) explains how to delete a WLAN profile in Win 10 (the trick is to press the "Don't save" button once):

https://praxistipps.chip.de/...ehts_11851

PS:

If it doesn't work then delete the WLAN profile again and then shut down the laptop. Then switch off the router… Wait 2 minutes… Switch on the router… Wait until the router is online… Now switch on the laptop and connect fresh to the WLAN.

If you always don't want to, then update the WLAN drivers on the laptop… Go to the device manager.