@Angela2720 It is an algorithm that Airbnb has actually had in place for a couple of years. It was instituted after some incidents in the US and Canada where there was violence at parties where people got shot and killed. Airbnb was getting really bad press over this.
The algorithm is supposed to take into consideration a number of factors- booking guest is under 25 years of age, trying to book an entire home, booking only for one or two nights, holidays, booking quite close to check-in date, and a few other things.
But according to many posts I've read, their algorithm is faulty and perfectly innocent, no risk bookings that don't necessarily fall into those categories can get blocked.