If your settings are correct IMO you should ask Airbnb to investigate the glitch and cancel the reservation penalty-free. Or report it as a bug on Airbnb Feedback
This is happening to me. Every day it gets switched back to 1 night minimum after I set it for 2 nights. I beleive they want to force everyone to accept 1 night bookings without saying it. I may switch to another platform if it keeps happening.