Hi Mary, well done on what you have achieved so far. What you are experiencing now is not an easy situation to fix unfortunately.
1.Airbnb algorithmns rightly or wrongly are preventing some guests from booking. Could be age related, they could be too close to you, they may not have good booking history, there's lots of factors. Airbnb are just not willing to take the risk. You could list on other platforms if you wish to get around this. But its a pain for guests who are genuine in intent and can't book.
2. Are there other cheaper priced competitors or hotels doing deals meaning you aren't seeing the business anyways?
3. You've only just started out as well, with 3 different listings, so your ratings are spread out over this. It's going to take time to build up your own ratings and the listing ratings. I'm convinced this has something to do with the algorithmns as well.
Kind regs MK