Why are all functions totally unresponsive.

The starter solenoid is energized by the CRANK RELAY located in the engine compartment fuse box.

Turning the key to the START position provides power to the CRANK RELAY and issues a start request to the Powertrain Control Module (PCM). The PCM inhibits the CRANK RELAY from energizing unless the transmission is in PARK or NEUTRAL.

You need to test both sides of the CRANK RELAY control (coil) input during failure. If no power, ignition switch related. If no ground, PCM is inhibiting crank.

Suggest you have ODBII history checked for module communication faults or other malfunctions.

Search range rover site for re-setting key fob procedure. https://www.6ya.com/callphilipforhelp

First put a booster pack or hook your booter cable on the car and there powerto the voyager take your remote and unlock the car if you dont have a remote simply unlock the rear door and passager door should remove the alarm good luck thans on using fixya

you need a battery connected for the ignition to work, lol..
sounds like there is a short somewhere - might need an auto sparky to look at it.

take keys out of car with you and lock all doors, then unlock door with the key and retry cranking vehicle

Check fuse # 8 -20 amp and look for the starter relay. The fuses and relays are in a black box under the hood near battery. The lid of the box will tell you every fuse and relay. There should be a spare fuse in the box or take one from another circuit and try to start the car

check the baterries in the remote key

take the positive side of the battery off for about 3 seconds and then put it back on to see if this will reset the security code

Either an interior light or head lights were left on all night, or there's a dead short in the electrical system, or... the battery completely failed internally such as a weak spot or defect in the plates. At any rate, it all obviously points to the battery. Replace the battery.

If the battery has gone dead, it could cause the security system to go into full lock-up mode. If it has locked up the accessories will work after the battery is charged back up , but the power to the starter will be cut off and it wont turn over. You need to do the 30 minute learn procedure. A GM dealer will print it out for you and you can do it yourself. It's very simple if you follow the procedure exact. hope this helps and good luck.