The contact owns a 2018 GMC Acadia. The contact stated that upon arriving at her destination, the contact shifted into reverse to park the vehicle; however, after parking and shifting to drive(D), the vehicle failed to respond. The contact became aware after several attempts that the transmission was stuck in park(P). The blank warning light was illuminated. The vehicle was towed to the dealer, who diagnosed a failure with the inline shifter wiring harness. The vehicle was not repaired. After investigating the failure, the contact related the failure to Technical Service Bulletin: 19-NA-206. The manufacturer was notified of the failure, a case was opened, and the contact was referred to the NHTSA Hotline for assistance. The failure mileage was 111,000.