Momentum 3 USB-C wired connection mode issue

Hello all,

I want to connect my Sennheiser Momentum 3 via USB-C to my desktop computer. However, when I plug the USB-C into the headphones, the headphones are not detected by my PC. I have also tried to put the headphones into "wired mode" as suggested by some other posts by slowly unfolding the headphones while holding the voice assistant button, but nothing happens and there is no confirmation from the headphones that they are in "wired mode". It's the same story with my phone so I don't think its a problem with my computer. The USB-C port works fine with my other headphones, and the cable charges my phone fine.

Am I missing something?

Cheers