Electronic OBD diagnosis can only go so far, if the original designers didn’t foresee certain problems and made no provision in the software or provided sensors for it then it can’t perform miracles. A lot of fuel system problems can go undetected by OBD systems because of this.
As such it can only find problems that it was designed to know exist, it’s not a crystal ball!
That is to say they’re not a useful tool, they can be extremely handy and can save shitloads of time in ruling out a lot of possibilities, but they have their limitations.
Cheap generic OBD scanners aren’t as good as the Pscan which is tailored to our cars various systems as it’s based on the factory T4 Techbook diagnostic system.
Modern fuel will go bad, sooner than the old stuff, and can destroy fuel pumps and clog filters, the fuel pumps in these are prone to intermittent failure anyway. And won’t necessarily show up on a OBD scan.
Also check your vacuum hoses a split or loose fit on the nipple can give no end of grief.
I doubt that it’s the immobiliser as the starter turns over.
Going on the information you’ve provided, shit fuel or vacuum leaks are the possibilities that have my instincts tingling
"Keep calm, relax, focus on the problem & PULL THE BLOODY TRIGGER"