Probably find its been lying for a while on the Dealers forecourt or he's fitted a gubbed battery to yours.
Get the battery charged and checked.
Range Rovers or for that matter Land Rovers don't like duff batteries and will throw up all sorts of errors.
This is from the handbook
Always adopt the following procedure,ensuring the cables are connected in the order shown below:
1. On the donor vehicle, connect one end of the RED booster cable to the positive (+)
terminal of the battery or the vehicle’s positive (+) connection point.
2. On the disabled vehicle, connect the other end of the RED booster cable to the positive
(+) battery terminal.
3. On the donor vehicle, connect one end ofthe BLACK booster cable to the negative (-)
terminal of the battery or the vehicle’s negative (-) connection point.
4. On the disabled vehicle, connect the other end of the BLACK booster cable to a good
earth point (e.g. an engine mounting or other unpainted metal surface) at least
0.5m (20 in.) from the battery and well away from fuel and brake lines.
Now start the vehicle with the discharged battery. Once both engines are running
normally, allow them to idle for two minutes before switching off the donor vehicle engine.
DO NOT switch on any electrical circuits on the previously disabled vehicle until AFTER the
booster cables have been removed.
Disconnecting the booster cables must be an EXACT reversal of the procedure used to
connect them, i.e. disconnect the BLACK cable from the negative (-) connection on the donor
vehicle FIRST.