Immobiliser Fault

[1944screen]

Hi on my 2012 focus, when I first go to it and switch it on the immobiliser light comes on, and the car won't start. Remove the key for 5-10 mins and it's fine as if nothing had happened, it's like this for the rest of the day. The RAC said it was the key reader coil, which I have replaced, not made any difference. Any thoughts, Mick

[Dagman]

Have you tried here?....
https://www.google.com/url?sa=t&;source=web&rct=j&url=https://www.fordownersclub.com/forums/forum/2-ford-focus-club/&ved=2ahUKEwjOoIODn4_tAhXIOcAKHQCvAXUQFjAAegQIGhAB&usg=AOvVaw1qJ1g7RvkXeHMeMSnY6GnO