@Bex0 Sorry to hear you're having such a difficult time booking a place, but quite honestly, your experience as a (potential) guest is far from unusual on Airbnb these days, and has unfortunately been a common experience for many searching guests for quite some time now.
I myself have been using Airbnb since 2010, with well over 50 stays as a guest, but after having 3 consecutive stays cancelled by hosts when I was travelling with my two sons in the summer of 2016, I prefer to use either hotels or rival platforms when travelling now. One of my stays (which had been booked months in advance) was cancelled by a Superhost - without apology or explanation - on the eve of the European Football Championships in Paris, just 12 hours before we were due to board our flight. (At the time the cancellation came through, I was running around like a blue-arsed fly, trying to get my own place ready for my 10 Airbnb guests who were arriving first thing the next morning)
Despite being a long-term Superhost myself, I received absolutely *no* help from Airbnb to find a new place - I was simply told by the CX agent to have a look on the site and see if I could find anything suitable, and Airbnb would give me 10% of the amount I originally paid towards a new booking. Not much use to me as by then, the very few listings that were left in Paris had doubled or even trebled in price since I had booked. Very stressful situation, and between that and the two further host cancellations that summer, I reached the conclusion that using Airbnb for future travels was quite simply too risky a proposition to bother with.
As regards your own situation - I fully agree that it's extremely poor form for hosts to have their calendars open for certain dates, unless they're 100% sure that they can host on those days. *However*, there is a known glitch in the system for quite some time now that allows guests to inquire about (and even Instant Book) dates that the host has blocked off on their calendars. (Plenty of posts on this CC about it). I know this to be true because it's happened to me at least 6 times over the past 18 months - 2 years. Luckily, I had reported the glitch to CX each time I'd received an inquiry for dates I had blocked, because when an Instant Book did finally come through for dates that I had marked as unavailable, and Airbnb tried to insist it was my error and deny there any such glitch in their system, I was able to refer them to the posts here in the CC, and the several tickets I had already opened with them, reporting the glitch, and they had no choice but to cancel the booking with no penalties to myself.
Also, the rolling calendar is really quite tricky for many hosts to keep on top of. So for example, when the host has their settings configured to only accept bookings in the coming 3 months, or 6 months or whatever, the new dates open up incrementally, usually at the very lowest price that the host has ever offered (and even lower, in some instances, especially if the host has ever used Smart Pricing), and many hosts find it extremely difficult to keep updating their prices with every single day that opens up, so find themselves being booked for dates in the future, at rates that would be economically unviable for them to accept.
And finally, it's an undeniable fact that Airbnb hosts in general (especially Superhosts!) have gained a really terrible reputation as nit-picky, entitled guests, who seem to get a kick out of reviewing other hosts harshly, and a great many hosts simply don't want the stress and hassle of hosting other hosts now, as they worry that their ratings and reputations will take a hit. So the many suffer for the actions of the few. Sad, but true.
I do hope you get sorted soon Bex but my advice to you if you want peace of mind - scrap the vouchers and look elsewhere. Best of luck to you!