From time to time There is a humming noise that happens up in the ceiling. I shut the furnace off to see if the noise would stop and it hasnot. Any thoughts on why this is happening? Do you think it is an HOA issue?

Is there a separate dwelling above you? If the noise is bothersome AND you are on good terms with your neighbor, invite them down to hear it and ask them to have it checked out. Otherwise, you may have to resort to bringing the issue up with the condo association.

You live there,, what's in the attic,, is heating system up there?, any plumbing? Rats with rabies? Snakes? I would be looking into it ,so you might nip-it in the bud before possible damage could occur,, is there a attic vent fan up there?