No rear park assist with accessory connected?

[cortez24]

Put my sled deck on my new ‘21 AT4 HD and connected the deck wiring to the 4pin connector in the box so that the clearance lights etc are controlled by the truck lights as they should be.  Trailering app detects that it’s connected and if I tell the truck it’s a trailer, rear park assist is turned off - which makes sense.

when I tell the truck it is an “accessory” the rear park assist is still turned off by default and CANNOT be turned back on unless the deck is disconnected from the truck.  Not sure why they didn’t make and adjustable setting for this situation, or just enable the rear park assist when you select that a accessory is connected.   
 

has anyone else had this issue or found a work around for it? I’ve searched the manual and all the settings menus and can’t find anything.