Last week I let another teacher borrow my microphone and when I plugged in back OBS wasn’t showing any activity. The mic still showed up, but the line monitor didn’t show any sound. Oddly though, the microphone still worked in other Windows programs. Just not in OBS.
After spending more time frustrated than I’d like to admin I noticed that I plugged the USB receiver for the microphone I use into a different port than it was in. Switched it back to its original USB port and OBS started seeing the microphone just like it should.
Got to like the simple fixes.