VP44 no longer delivers high pressure

Hey guys.
Bernie's tow truck has broken down . It's a MAN F 2000 with a 4-cylinder engine. TDI, 4.6 liter, 186 horsepower, year 2003.
I am sorry, but I am unable to access external websites, including the one you provided. Therefore, I cannot translate the text from the German website into English.

It stalled while idling and now won't start.
Today, we checked the following: We loosened and cleaned all the injector line union nuts at the injectors = the pump is working properly and in sync with cylinders 1, 3, and 4, and cylinder 2.
Then we removed a fuel injector line and installed it in a way that allows us to screw in a test nozzle. We vented the ESL (Electronic Stability Control) system, tightened the test nozzle, and started the engine, but nothing came out.
I don't know anything about the VP44 and I don't know where to look .
Buying a new one isn't really my style.
Can any of you give me a tip?

Bosch Part No. 0 470 504 017
Usage No. VR4/4/65M1200R1000

Best regards, Kurt.

"If it suddenly stops working and then refuses to start again, it's usually the control unit. However, you probably won't be able to access it without a VAG-COM compatible diagnostic tool." Bosch service or brand new.