I don't know who you are talking about, but this sounds like the transfer case actuator, or the front differential actuator is not working. Here is the location so you can replace it. I would see if you could hear the actuators working in each location when you use the 4wd switch. Check out the images (below). Let us know what happens and please upload pictures or videos of the problem.
Images (Click to enlarge)
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Thursday, January 19th, 2023 AT 10:30 AM