td4 not running

Hi,
got a 53 plate td4 (manual) drove the car Wednesday was all fine parked up and went to move a few hours later and now wont start or run.
I've tried easystart but once its burnt that it dies!! I've had my injectors refurbished 18 months ago and ive done a leak back check and all fine today. (I did have one injector stick open last year causing a non starting fault but that was replaced and has been fine since)
I have looked at forums about the rail sensor and the pump reg.
What is this o ring that splits as I cant see any split o rings on the reg.
next thing to do is replace the rail sensor

Any help would be great, typical it happens a week before race season need the freelander as my tow car!!

New sensor didn’t cure it

Problem is usually the connector more than the sensor.
There is an overlay harness available

Had a friend come over with a proper diagnostic tool not my cheap eBay one! Pressures all fine but cam sensor kept coming up.
Replaced with a Vemo one all fine now!
Will probably buy a genuine sensor at a later date, never had much luck with cheaper brand sensors