Hi @Skye68 I hope you’re well!
Just have a polite chat with the potential guest to understand the reason why- you’ll usually get an answer that explains that a partner or friend has been the person who’s booked previous trips they’ve been on- or perhaps they’ve joined Airbnb but not got round to booking a trip yet for whatever reason, maybe they’ve just been window shopping.
Something as simple as “I see you’ve been an Airbnb member since 2017 but are yet to have any reviews on your profile, have you used Airbnb for a trip before?” Should elicit an answer that will help you gauge.