2001 2.8 V6 P1479- Brake Boost Vacuum System: Mechanical Failure

I ignored this code for a while, but ever since the vacuum pump relay started clicking like crazy, I decided to take care of it. I first replaced the 373 relay, that didn't fix the problem. I had the car at a shop a two months later to have the CCT gaskets/seals replaced, and the mechanic diagnosed it as a bad vacuum pump. Rather than give him $500 to replace it, I bought a good used one off of eBay and replaced it myself. The replacement went smoothly, but it still isn't fixed.

I used VCDS to test the system multiple times, and basically when it tests the system, the pump doesn't turn on, even when the pressure is at 1,005 mbar with the engine off.

What's next? I know there's a lot of threads on here regarding this, but the majority of them are for the 1.8 T, and the ones that I found for the V6 weren't very useful to me.