@Bonnie433,
This is awkward.
If the guests are a couple only, and you are fairly sure they aren't throwing a party...then I would just drop it, don't mention anything because IF they contact support you can almost be certain your listing will be shut down.
Not worth the loss of income, in my opinion.
If the guests reach out to you with any questions during their stay then you could subtly ask if they were aware that something is blocking your camera and then take this opportunity to give them 24 hrs notice that youll be sending your handy-man over to check it & unblock it.
There is an Airbnb document that states what Airbnb does & does NOT allow, and blocking cameras is on the list. I'll look for it and will reply with it below in a few min..
But I wouldn't bring it up to airbnb because again the new support reps are quick to shut down our listings first, and investigate later...much later.