Why is my mircrophone not working?

Hey, I am using the astro a40 TR and the mixamp that came with it but for some reason my microphone is not being picked up anymore (it used to work fine).

Both the headset, the mixamp and the microphone still work as I tested each individually but together the mic drops out.

For example, if I plug in the heasdset with mic directly into the pc then I can either listen (audio out) or use the mic (audio in) so both work fine. If i plug in my default phone earbuds into the mixamp, both sound and mic work fine on the pc. However, when I plug in the headset with mic into the mixamp, only the sound works on the pc and not the mic.

I would think it could be the cable but then why does the headset + mic work when I plug it directly into the audio in/out ports of the pc. I am very much confused about this problem and I am not sure which steps I should take next to find the real issue.