I had the same issue with a 2017 RR Sport. The AEB never worked, even though my previous Merc the warning would go off at least once or twice a month, and the braking kick in a few times as well. In similar situations the RR would not even give a warning. Went to one dealer multiple times who kept saying there was no fault, even escalated to Land Rover Australia head office with no response. Took it to a different service department for servicing 4 days ago and they found the issue, updated the software, and re-calibrated the system. Within 3 days, the system had already activated once (with a nufty braking hard in the middle of the road for no reason). If one dealer can't find an issue, try a different one. I believe there is also a recall for some MY18 models for AEB, but I wouldn't be surprised if the issue actually exists for MY17 as well.