Hi all,
Here is my experience with this, which may be helpful. I got this message on my MY2017 DS with 40,000km on the clock last Friday, with my son driving, halfway into a 500km trip from Sydney to Guyra on a backroad. See attached photo. It said "No engine restarts in 870km. Diesel exhaust fluid dosing malfunction".
I called the service department at my LR dealership in Sydney, and they advised that the 870km figure would reduce rapidly, and that once it fell to zero I would not be able to restart the engine. Their advice was to park, and they would tow me back to their workshop, the most probable causes being a broken wiring harness or a malfunction of the DEF injector. When I said I was 200km from Sydney, they advised me to call Roadside Assistance instead. However, roadside assistance were not interested as the vehicle had 'not been immobilised' yet.
We decided to press on (really we had not other option) to the next town, Walcha, about 120 km away. While passing through that town I got enough internet connectivity to read through the entries on this thread, and was encouraged to read the one from sodum, who had parked at a pub after getting the message, and returned to his vehicle to find it (the message) gone! I hoped that that would also apply in our case.
At the next town, Armidale, we decided to change drivers for the remainder of the trip without stopping the engine. As I got in though, I absent-mindedly pressed the engine start button, which of course stopped it. Worried that the vehicle might not start again, I quickly pressed it once more and the engine started. To my relief the message had gone. I checked for any warnings under 'Vehicle Information', but there were none. The message has not reappeared, 600km later. So it appears to have been a computer glitch.