4WD not working?

I see you posted this twice, so I'm going to get you started, while the other experts will still be able to see you other post and have a chance to reply. By now you know replacing random parts is the most expensive and least effective way to diagnose this. We've all been there. Instead, I can offer two places to start. The first is your observation the 4wd light doesn't turn on. That points to fuses as the first suspect. Look for M15 and J11 in the under-hood fuse box. Those are 20 amp / yellow and 30-amp / pink, but the aftermarket drawings don't show their locations. You'll have to use the fuse box cover and a magnifying glass. to find them. Be aware fuse M15 includes power seats and the instrument cluster, so if those are working, that fuse is okay. I have the system diagrams but I'll need a little time to format them for easier reading. There's two different transfer cases available. You'll have to figure out which diagram is for your truck.

The next step is to have the diagnostic fault codes read and recorded. This article shows how that is done: The "Service 4wd" light is what tells us there are codes to be read.

https://www.2carpros.com/articles/can-scan-controller-area-network-easy

The people at many auto parts stores will read them for you for free, but often they can only read them in a few computers. You may need to visit a mechanic for a complete scan. That will list all the fault codes in all of the computers. It only takes a few minutes.

Once you know the exact fault code number(s), you can go here:

https://www.2carpros.com/trouble_codes/obd2/p0300

to see the definitions, or I can interpret them for you. Be aware those codes never say to replace a part or that one is defective. When a sensor or other part is referenced in a fault code, it is the cause of that code only about half of the time. First we want to rule out wiring and connector terminal problems, and mechanical problems associated with that part.

Let me know what you find with the fuses and those fault codes.