Range Rover P38 Navigation, Audio and onboard computer

Hi all,
I'm new to LR family and just brought home a 2001 RR P38 4.6.
Bought it for the light offroad trips and now learning thing about how to use it.
Accordingly to it's age there is no manual or paperworks comes with car .
I have a navigation suddenly with limited functionality - i can select only "GPS Navigation" or "Monitor Off"
There is a "onboard computer", "Code" and "SET" as well on the screen, but it is not possible to select.
Also radio and CD Changer seems does not work. There is both ACC+ and Memory + and Ground on the connector, and fuse is OK on radio.
Would really appreciate if experienced users will share knowledge with me, how to activate all functions of the navi unit and switch radio on.
I believe i'm doing something wrong.

If you want manuals then you can do no better than download RAVE. Probably a link in the Technical Section or try landroverresource.com.

Don't have that model but sure someone on here will know. @martyuk is pretty hot on the stereos.

Thank you Grrrrrr,
unfortunately none of these resources have any helpful information related to the described problem.
Probably visited all the possible pages. So hopefully @martyuk will see this thread

The radio I have is Alpine XQD101550LNF - maybe somebody have a schematics for this? I'm under impression the problem might be in the radio itself - does it linked to the navigation system somehow?
I also managed to get the CODE be active on the navigation screen couple of times yesterday, but when I enter radio code it offer 2 options -Change and Deactivate. either of this make the code section inactive again.
Does the navigation unit have it's own code or it is just a display and all the brains are in Radio or rear navi unit?

The navigation computer you have installed in the car does not have the correct software for a P38. I suspect its from a BMW E38/39/46 etc or it could possibly be from an L322 range rover. The greyed out options are not available in a P38, your also missing ofroad navigation.

I wrote a little topic on this a year or so ago whilst dealing with my last P38

https://www.landyzone.co.uk/land-rover/p38-navigation-repair-guide.298587/

Essentially first of all find out if you have a Mk3 or Mk4 computer in there (I suspect it will be a Mk3 which is what it should be) and then see if you can find the hardware version or any part numbers on it and that will tell you what it originally came from. Once you have done that, there is a link to Navtvman a guy called andy who can reinstall the P38 software onto some hardware (even if it came from a BMW etc) as long as its the correct hardware version