Hello,
We just wanted to share an issue with Instant Book in case other hosts are experiencing the same problem. We had Instant Book on, but required a verified ID from guests in order to Instant Book. We had 4 guests recently who used Instant Book without having a verified ID. We had AirBnB cancel two of them, but were able to speak to the others and get them verified. AirBnB is aware of the issue and has their technical support team looking into it. We have turned Instant Book off in the meantime.
If anyone else is having the same issue, you may call AirBnB support and ask for an update on Bug Report #476813.
Jon and Sam