2011 Jeep Commander - Transmission won't give reverse

2011 jeep liberty no revers

your reverse solenoid could be bad.

where is the solenoid

Inside the transmission. I am not familiar with your vehicle, but when you drop the transmission pan you should be able to see it. but there will be other solenoids too for each gear.

Ask shop to make sure reverse activate signal is being sent to transmission. Problem could also be in gear selector switch/logic.