Agree with you on ranking. That's the most probable reason of not getting bookings. But I don't think lowering a listing's rate might get it closer to the top.
In fact, the listing search is the weirdest thing about Airbnb. For example, I've been renting my flat for more than 2 years and when I try to search it on the map, I need at least 6 mouse scrolls for it to appear on the map, while other listings (with much higher price) in the area are visible immediately.
I read the official Airbnb guidance on how to improve a listing's visibility. The most important factors mentioned were: rating (the higher, the better), availability (the longer the calendar is open, the better), absence of booking declines (the less you decline guests requests, the better).
I tried lowering the price with and without applying Airbnb promotions, but it doesn't work. On the opposite, a too low price might be the reason why potential guests would be more suspicious, thinking that 'something isn't right with the property'. I guess that's the marketing psychology, people trust you more if a product price is not too high and not too low.
Unfortunately, despite all my efforts, it's been more than a month my apartment not getting any bookings. Hope things get better though.