Hi Kent,
Thanks for responding. So, when I stream I am using a USB Capture Card by way of an HDMI splitter. This splitter is a hub for 3 HDMIs, one from the XBOX to the splitter (IN), two HDMIs go out, one to my TV and the other to my Computers USB port (with the capture card USB stick plugged in).
I actually don't know if there's another way to get the audio from my XBOX to go directly into the computer as even with this method I don't hear people talking in game chat on the stream, only in my controller headphones. I'm not monitoring the XBOX audio on my computer other than watching the stream on my Twitch channel on my computer (occasionally I'll turn up the speakers on the computer to confirm audio is working or check the levels on OBS), but I'm playing with an XBOX controller with my headphones plugged into the controller.
Yesterday, I was able confirm that the in-game chat audio was working again. I played with more random people, and while my speaker icon did not light up or change (it just showed as if I have a mic plugged in, but am not talking) I chatted with someone the whole game and asked them if they could hear me and they said "Yes".
The only things I did prior was replug in all the HDMIs, choose Restart My XBOX from the Xbox menu, changed Audio Output settings on the XBOX to Stereo Uncompressed and turned off any special audio settings for headphones by changing Headphones Output to Stereo Uncompressed.