Bmw x5 e53 m57 (52 plate), just wont start

[Jmh474]

This is going to be a long one sorry

So im in the middle of purchasing the car of my next door neighbor, he used to work a lot on cars and he not in the best of shape 😔 one of the nicest blokes i know, i myself not got that much knowledge or money to get the car sorted.

So i started out grate hes selling it to me at a grate price and even letting me pay him here and there as im out of work (as i care for my autistic son) so not really got the cash to splash.

So we was looking over the car and everything was running and sound grate then all of a sudden it just cut straight out and would not turn back over.

He got his diagnostic laptop and had a look for me come up with fuel rail pressure sensor error so we replaced fuel filter still the same, so then replaced fuel rail pressure sensor and this cleared the error. But still not turning over.

All fuses check out fine

Done a injector leak back test that was fine.

Cam and crank sensors test out fine.

Fuel pressure is about 380 cant quit remember the right number.

We've use a sound scope and can here the injectors clicking.

We've sprayed some easy start and it will start up for about 5 seconds sound like st then cut out.

Now there are no obd error codes and the engine still wont turn over, the thing we cant understand is it just cut right out no splutter or anything just turned off

So is there anything we've missed or any advice anyone can offer thanks