In the last 30 days, we’ve noticed 50% of listings like yours added nights.* Doing this with your home could help make it more attractive to guests comparing their options.
What's the full message @Amy-And-BJ0 - is it just asking you to open more nights on the calendar?
Airbnb is always pushing hosts to add more availability, and like @Joelle43 I'm also not aware of a new feature, so I'm just guessing maybe it's just asking you to unblock as many nights as possible?