@Janine243 when you decided to set up your STR business I can only think you didn't check the terms of your HOA lease, to see what conditions you might need to comply with, as if you had you would have known that you needed to register your guests (not tenants) in advance of their stay and could have done this, thus avoiding the fines.
Many HOAs don't allow STRs full stop, so you are fortunate that yours does. (but obviously not fortunate that you didn't check the terms of your lease and thus opened yourself up for the fines).
You can't get legal advice from a forum - this you will need to get from a lawyer with experience of HOAs. You would need to get a quote from them so you can make a decision on whether it would be cheaper to pay the fines and comply going forward, than it would to pay your lawyer fees and fight your case.
Are there others doing STRs in your building and are they all complying with this lease condition?