Elgato refusing to pick up game audio on PC

I'm seriously confused and if anyone can help me I'm forever in your debt.

So my Elgato works like a charm for every device except my PC. It picks up game audio no problem on consoles, and I can do everything else like commentary with no issues.

HOWEVER - when I set up to record PC games, everything EXCEPT the audio records perfectly. It picks up my commentary, records a flawless image but theres just no audio.

I literally cant record any audio from any source using my PC (via the Elgato).... Games don't record audio, music player doesn't, web browsers don't...

I have tried everything. I've opened sound settings and changed the playback and recording settings to what I believe are the correct options (stereo mix is default device, set to listen to me as I have a wired headset and yada yada yada)

I've tried every single combination of playback settings I can, in case I'm missing something.

I've tried using Elgato sound capture as a separate audio setting app thing, and that doesn't pick up any audio either no matter what settings I use.

Intriguingly enough, OBS records absolutely everything (except games obviously)...

It records the audio from my PC absolutely fine so I just don't understand why my Elgato isn't picking up the audio?!

I don't understand.

Since OBS picks up every kind of audio from my PC, it makes me think that the lack of audio is due to my Elgato settings, but I have literally tried EVERYTHING I can think of to get it to work. It just doesn't wanna pick it up.

Anyone got any tips for me to try? Thank you in advance :)