If the actuator is stuck, it won't engage the axle. When the transfer case is placed in 4WH or 4WL, the electric motor actuator turns on and builds pressure. When the pressure reaches the specific amount (within seconds) the actuator engages and locks the differential into the drive mode.
You indicated the motor is running for a couple of seconds, so either it is stuck, something is preventing the air to build pressure, or the actuator itself is bad.
I attached a pic below of the air inlet union and hose. Inspect those to make sure nothing is damaged or rusted shut.
Let me know.
See pic below.
Friday, January 21st, 2022 AT 8:01 PM