Check Rear Gate Latch Switch
WARNING: This page is about a different car, the 2015 Subaru Outback and 2015 Subaru Legacy. However, it is still accessible from the selected car via links, so may be relevant.
Refer to "Rear Gate Latch and Actuator Assembly" in "SECURITY AND LOCKS" article. <Ref. to ACTUATOR , INSPECTION, Rear Gate Latch and Actuator Assembly.>