First check to ensure that you have 20-22" of vacuum produced by the vacuum pump. You can check this by hooking up a vacuum gauge or Mityvac to one of the ports on the main vacuum tube going to the brake booster.

If you have good vacuum being produced by the pump, then check the engine shut off valve using the Mityvac to see if it actually works by starting the engine and applying vacuum to the shut off valve using the Mityvac. The engine should shut off immediately. If not, your shut off valve is defective.

If the shut off valve is OK, then you will need to check the many other places for vacuum leaks individually using your Mityvac (door locks, climate control vacuum pods, fuel door vacuum actuator, trunk lock actuator, EGR valve, etc.). Occasionally the vacuum reservoir will also leak at the hose entering the reservoir.