My money is still on air and/or connector torque issues. The modern diesels require such high pressures that very small leaks will reduce pressure to the point where there's no ignition.

Assuming you never touched the metal fuel line end that actually connects to the hpfp, I would revert again to loosening the #14 nut on the fuel accumulator. Bleeding/cranking should get fuel bubbling around the threads - though as I recall it did take a total of 30-40 seconds of cranking before getting the air out and fuel coming out. Then you'll want to make sure all of the other twelve connectors are torqued correctly. And then (in my case at least) it will take another 30 seconds or so total cranking time before it starts.

Only after doing the above would I start delving into other aspects of the system.

__________________
Stephen
2010 e70 35d- now driven by son #2
2005 e53 3.0 - now driven by son #1
2021 G05 45e PHEV - now driven by me
2008 ML320 CDI - driven by wife