Also if you haven't read it this thread has great information on rebuilding and reinstalling the rear actuator.
https://forum.ih8mud.com/threads/locker-actuator-rebuild.551069/page-2
Have you tested for 12v at the plug just before the locker? It's short duration (i.e. voltage is only present briefly) when it locks/unlocks so it helps to have someone turn the switch while you verify 12v. Attached is a test sequence in the FSM. Would at least rule out the wiring.