Isuzu NPR Vacuum Problem


New Recruit
I'm new to this forum site.

2017 Isuzu NPR, 6.0 Gas (L59), Single Cab

I have the "Brake Booster" light on, with the electric vacuum pump running. I replaced the electric vacuum pump, the mechanical vacuum pump, and the brake booster, along with testing the whole system with a smoke machine (no sign of leaks), and it's still not building vacuum from the mechanical pump, and the pump is working properly (check valve works). I'm not sure where to go from here.

Any insights are appreciated, thank you.