I changed the price on a specific unit, but the price on Booking.com didn't update. Why is that?
The specific unit is not directly connected to Booking.com, and price changes on it do not reflect in channels. If you would like to change the pricing of the multi-unit, click on it in the multi-unit calendar page and update the pricing directly.
I chose to auto-assign reservations at reservation creation, yet I still see unassigned reservation from time to time. Why is that?
Unassigned reservations can happen if you have open availability over a few days, but not on the same listing. For example:
As you can see, all three days have availability, but if a reservation were to come in for all three days, the system will have nowhere to assign it to, and thus will leave it unassigned. While it takes some time to get used to it, this is actually a feature that allows you to get more reservations and increase occupancy, since it allows you to get reservations you couldn't otherwise accept. What you should do in these cases is relocate one of the existing reservations, creating consecutive availability and then manually assigning the new reservation.
What is the benefit of auto-assigning 2-3 days before check-in?
Auto-assign works best the more information the system has. Close to the check-in time, the system knows more about the expected reservations, and can reduce (although not eliminate) the need to manually shuffle listings around.