@Emilia42- Thanks for setting me straight on the "Reserve" feature (which does seem more like a bug, in that it IS confusing).
@David-Henry0- Emilia has provided some good reading. It could well be the two guest-side cancellations that have put you into Instant Book jail. Totally unfair, but once the algo gets something stuck in its craw, you're done for. CX will not help you get it re-enabled either. I'm sorry that this has happened to you. I know from experience that it sucks - especially when you're doing everything you possibly can to build up your ranking.
When this has happened to others (including me), there's a waiting period of about 3 weeks, during which you must accept every crap request that comes your way if you want IB re-enabled.
Many hosts don't use IB, finding that they're far more comfortable vetting guests themselves through communication. I know it's kind of a pain, when you're used to just having the bookings roll in, with no effort on your part. You may find, though, that it gets less cumbersome as time goes on and that you actually prefer it.