Same issue, W11, new version of audition. I am not able to record anything with the stero mix. Even my own recording, being played with VLC or any other player on my computer, is not being picked up.
I am sorry that you're having this problem. There's a workaround for this, provided that you DAT or modern audio board. I have the Rode 2, and I am running Windows 11. Windows 11 routes my recording devices to record directly from the Rode device. The Rode 2 uses SD card, and I am able to record directly from the internet and other audio outputs. Perhaps, recent updates from Windows 11 or Adobe has disabled this feature. Adobe apparently seems to be mum on this topic. Anyway, I hope this helps. Good luck!