I got this message on my 2020 Chrysler Pacifica PARKSENSE UNAVAILABLE SERVICE REQUIRED. What could the problem be?

IT means that the SELF PARKING system needs ATTENTION! GO to the DEALERSHIP and ASK THEM or call CHRYSLER or even read your MANUAL! THEY make them for a REASON! MAYBE a RELAY! MAYBE a STEERING issue! MAYBE a FLAW! MAYBE there is a RECALL on it! THAT IS FREE. DEALERSHIP TIME!! 

with new cars could be anything but more than likely one of the round park sensors on your bumper

Take your car to the dealer.  It is under WARRANTY.

The problem is a loose nut behind the wheel

This is what the manual says

If the "PARKSENSE UNAVAILABLE SERVICE REQUIRED" message appears in the EVIC, see an authorized dealer.

Get a $4000 mechanic's scan tool from the dealer and read the codes for the rear parking assist.

As it's still in warranty why don't you take it to a Chrysler dealer? It's obviously a fault with the electronic parking assistance.

Spam, spam and spam...get them all the time....I just say I don't do anything over the phone......