My first thoughts were similar to what Will said about comparing the cover plate to the oil filter head to see if the passages are any different.
You've probably compared the gaskets and part numbers or Jeff's done so already but I attached a screen shot from QuickServe for my engine. The gaskets appear to be the same based on the images.
Is there anything inside or behind the supply port in the cover plate that would prevent feed to the turbo(s)? I imagine it's not a blind hole that requires drilling and tapping. Surely you'd have caught that. Still strange that the gauge registers pressure when cranking but not running.