Priceline Reservation & Preferred Service

I never use a travel agency to book a car rental, but this upcoming trip, Autoslash was significantly cheaper.

That books through Priceline.

I entered my Avis Preferred number on the Priceline reservation but it doesn't show up in "My Rentals." If I look up the reservation with the confirmation number it does exist and it seems to show my Avis number, but just isn't in my app/rentals.

Any idea why? More importantly -- do you get the Preferred service with these priceline reservations?