I have a 2010 4x4 platinum. I can change the knob to 4x4 or 4x4 low and it goes thru the process and say its in 4x4. However it wont actually engage. I never noticed this until now...when i need it.... Sent from my SM-G955U using Tapatalk
Without being there my guess is the actuator motor in the transfer case. Sent from my SM-G930P using Tapatalk
Actuator or the check valve is plugged. Vac line could also have popped off the IWE at the knuckle. Double check that. If the lines are on, see if you can feel any vacuum and work your way up to the actuator. There is a small check valve that also causes issues, $13 part from Ford.