Is this via NDI? I don’t think CH outputs the audio on NDI for some strange reason. So I had to use something else to get audio into OBS.
In my case, I feed the mic into Adobe Audition to do nosie reduction, then send the output to “virtual cable”. This also inserts delay into the audio stream. I then get OBS to listen to virtual cable PLUS get CH to listen to virtual cable. (Hmmm, not at computer, cannot remember if CH listened directly to mic...). I then use NDI to feed video output from CH into OBS separate to the audio. (OBS you can add multiple sources.) I think I also added a delay to the video in OBS to get it back in alignment with the audio (because of the Audition noise reduction processing delay).
If you don’t get it working I will try and get some time on the computer and write down exactly what I do. I don’t recall where I got virtual cable from (I might have bought it for like $10). It really helped gluing all the parts together For me.