My MPi's starter functioned even when the alarm/immobiliser was activated and, indeed, it would start and run for a few seconds before dying from lack of fuel pressure. So it's unlikely to be that.
Do you have a voltmeter on the dash?
Can you clarify what you mean by "SRS light goes out on button"?
SRS light should come on when the ignition key is first put in the 'On' position, while it runs through its self-test and then goes out, if test is successful.
Have you tried turning on the headlights and turning the key to 'Start'? Do the lights remain on, dim or go out?
Edited by Quinlan minor, 25 March 2020 - 11:40 AM.