Thank you so much! Disabling the IR camera didn't immediately solve the problem - but it led me to notice that Messenger was auto selecting a certain camera from the options within Chrome itself. The camera and microphone drop down menu within the Messenger call was unselectable, so I couldn't change the camera Messenger was attempting to access - so I looked in the Chrome settings, and, alas, a camera option by the same name was there. By activating that camera option (instead of the normal camera that was selected previously) and restarting the browser, everything is working now!
Interestingly, now, in the Chrome settings, there is only one camera option, just the normal camera (which was selected before...). So I don't have any record of what I changed it to to fix the problem, unfortunately.
Thanks very much for your help. Now I can delete the Messenger app from my computer... which I'm not a huge fan of!
