@Claire314 I know it is so frustrating for a host to lose a booking because someone has not set up a profile and therefore cannot book. There is not much you can do to help except to give contact information for Air BNB. I dealt with this situation when a friend of a friend suddenly became stranded in my area and needed to set up a profile. Takes time.
I wonder if someone is going to book 20 days that they would not have better advance planning. Perhaps it was an emergency. In my situation, I insisted on requiring an Air BNB booking, but you might want to have an alternative way to book guests as a private exchange. There is no Air BNB involvement, but people have been hosting outside of Air BNB for a long time. Just do not expect any of the support systems of Air BNB to be involved.
