2016 Focus Not Starting After Battery Replacement

[tbone455ci]

Hi all,

Replaced the original battery with a new one but now the car won't start, not turning over, no clicks from the starter.

Feels like it's immobilised...all lights, wipers, windows work. It's a 2016 1.5 diesel Focus.

When I put the ignition on the battery light comes on for a second and then off. I get the service Car Now warning in red, Hill-start Disabled warning in orange that wasn't on before. 

I've tried two methods to reset the BMS (battery monitoring system) but don't get the battery light flashing when doing it to indicate its reset/

Plugged in my OBD reader to read/clear codes and it won't connect to the ECU, works on other cars?

Tried resetting the immobiliser with the key turned right then left for 30 seconds but still no start?

Has anyone else had this problem or any advice?

Thanks for any help

Terry