The measured pressure is less than the lower limit set for the application.
Check supply pressure to manifold
to ensure proper air pressure is being delivered to the manifold. (Supply pressure would have to be greater than the pressure being monitored in port 2 of the valve.)
Check all tubing and or hose connections
from port 2 of the valve for possible leaks or disconnections.
Check for leakage across the cylinder piston
If valve is operating a cylinder/actuator (You may hear of feel air coming out of the manifold exhaust port, when all other valve functions are at rest.)
Operate the manual override
on the valve to ensure valve/spool is shifting completely. (An incomplete shift could result in excessive leakage into the exhaust port of the manifold.)