Gaming headphones with UR22C?


I am having trouble with running my gaming PC headset via UR22C. Headset consists of two 3,5 jacks, one for headphones and one for mic. Headphones via 3,5 -> 6,3 reduction are working well, though I cannot run mic via any reduction.

I already tried (most probably) all possibilities, to use stereo reduction to 6,3, mono reduction to 6,3, to use XLR reduction from 3,5 -> XLR, but non of them seems to work as input. I tried to insert guitar with mono 6,3 cable and it confirmed functionality.

Now, am I doing smtg wrong, or such setup will not work at all?

Thank you