I think I just had this same situation and I believe I fixed it....
About 2 weeks ago got about 18" of snow.. lost power and needed to go to town.. .drove out of my driveway and got stuck in the middle of the complete flat cul de sac.. wet packing 18" of snow... both rear wheels turning, no front wheels turning.. kind of embarrassing. Went and got my bronco and pulled the raptor back into my plowed driveway. drove back toward my garage and my rear wheels were spinning as I tried to drive over the hump to get into the garage.
No codes, no errors, no indication inside my truck that anything was wrong. My only diagnosis was no front drive.. and was wondering how expensive this was going to be.
I have a Gen 1... 2013 with ~80k miles
looked through this thread and bunches of others and found people pointing to the Vacuum system and possibly the solenoid.. that is less than $20 from Amazon, worth a shot.
I replaced this part - 4x4 Vacuum Solenoid Purge Valve 4WD Locking Hub Vacuum Solenoid 7L1Z-9H465-B
The part came in ~ 3days, took ~5 mins to swap out... I think its fixed....
Pre swap of the solenoid
Drove into my cul de sac where there was a pile of snow.... backed one rear wheel into it until I was stuck and rear wheel was spinning... front on dry pavement... shifted into 4wd.. nothing changed.. rear spinning, couldn't back up.. front not doing anything..
swapped out solenoid...
same deal.. backed in, rear spinning... shifted into 4wd... was able to back deep into the pile and certainly seemed like the front was pushing.
so... two questions...
1 - was that a fair test
2 - did I likely fix my problem, or is there something else I should worry about or test?
FYI - snow pile is finally gone, so can't test that anymore.
Any comments, concerns, questions, would be greatly appreciated... hopefully this is helpful?