2007 should have "live axles" up front, so no locking/unlocking hubs, which is good, those "auto" hubs only worked for a few years new, then they were a pain in the backside.
So you really only have the electric shift motor and its control module.
Shift motor can get dirty and finicky, tap it a few times with a hammer and see if it starts to shift into 4WD again.
These can be removed and cleaned.
Module will have 4X4CM in large letters on it, on ours it can be on the back wall of the cab but not sure on yours.
This can be installed in place of the electric shift motor, for manual operation.
But you do have to get under the vehicle to use it so.............