As Carl said - have you checked the fuel pipes are fitted the correct way?
Pipes marked with blue are return, black are supply.

Blackened components in the tank are common on these.
The fuel can reach temperatures of 90C and turns the fuel tank into an aquarium.

The symptoms you describe of flow with no pressure & no relevant DTC's are symptomatic of the return & feeds being switched. The most common place for this to occur is at the fuel delivery unit.

There should be a min of 0.5bar from the fuel delivery unit in the tank to the fuel filter.
There should also be 0.5 bar after the filter.

Filters are known to block.

Tandem pressure needs to be checked at the allen bolt port on the tandem pump with a banjo adapter.
Roughly 3 bar at idle & 10 bar when revved to 4000RPM are healthy pressures. If using an undamped gauge the needle will be break dancing around the dial.