The reason
@neilly asked about the vehicle and the engine, and I'll ask about the year of manufacture is that there was some confusion regarding code readers, particularly for the diesel Discovery 2 until mid-2004 when the Disco 3 was released on the unsuspecting public. Until then, only the petrol versions were compatible with OBDII protocols. I'm unsure whether that situation applied to other Land Rover vehicles including Range Rover.
When you're investigating the market possibilities, do bear in mind that the sellers will never mention the differences between petrol and diesel, consequently many people do get caught out when they buy such items as the iCarSoft device.