Serv4WD, 4WD Unavailable

Yesterday I took my wife to the beach so she could learn driving around in the sand, using the 4wd. Needless to say, she LOVED it. She had a blast! However, after 30-45 minutes of goofing around in the sand and after me getting back in the driver seat, I got the error “serv4wd” and “4wd unavailable.” So I got stuck and bottomed out since only my front wheels were working. Couldn’t get back out on my own, a nearby dude helped me out with his Chevy Silverado. The drive home from the beach is about 40 minutes and the compass worked as expected.

When I got the message the first time, I shut off my engine for a few minutes and re-tried. The 4wd came back on, but only briefly then same message again. I shut off the engine once more and waited longer but still I ended up in the same predicament. Anyone experience anything similar before or have any input? I feel I may have overheated the transmission, engine temp was normal. When I would get the message, the transmission would shift out of gear and the engine would rev up while I reacted and released the gas pedal.

Thanks for reading!