2015 Crewmax SR5 4wd - C1201 and U0114 error codes no 4wd

Good morning,

I just bought a 2015 Toyota Tundra 4wd SR5, after Hurricane Ian flooded my 2006 Tundra. I'm running into an issue where I can't get the 4wd to engage. While driving the truck I've tried turning the 4wd dial to 4wd, and there is a clunking sound and the rpms go up, but the 4wd indicator keeps blinking. If I try shifting to 4wd low there is beeping (which I think means the 4wd isn't engaging).

So far I've done the following:
1. While in park - the same clunking sound, but the 4wd indicator keeps blinking.
2. While in neutral, both moving and standstill, and still no joy. If I am rolling forward in neutral the truck decelerates and doesn't coast as easily.
3. I've tried engaging then driving and reversing, but the light still flashes.

I took the truck to the mechanic and he gave me the codes C1201 and U0114. I've done a little research and it looks like those can be for a lot of things.

Any suggestions on where to start the diagnostics? I read the info sixweeds provided about the Transfer Case Actuator repair, but I'm not sure if that's the same for the 2015s.

Thanks for the help and advice.

Also, where do we get service manuals for tundras? I remember seeing there was some sort of toyota website you had to subscribe to?