I have a clicking noise coming from where the air filter is in the hallway

When the unit is running or is it constant?

Take the filter out and stick your head in to look up in there with a flashlight while it’s running. Might just be something like a piece of tape flapping.

I once had a rhinoceros beetle find it's way into the wall space above my air filter and was prying at the filter to get out. Sounded like a clicking and couldn't figure out what the heck it was, but it was late and I wasn't too keen on pulling the grille down and having whatever creature it was fall on my face. Found it stuck between the filter and the grille the next morning. Never expected to find one of those things in my house.

Anyway, doubt that's what you have but seemed like a good place to tell that story . If it's coming from where the air filter it's probably not a big deal. Maybe the filter is loose and the air flow is making it rub on something. Or maybe there's a monster beetle stuck in there.