Couple things to check:
- solenoid is plumbed in the correct direction (if you are using the KOP festo, in is port 1 and out is 2 and 4)
- try manually actuating your festos to see if it is a programming/elec. problem or if its a plumbing issue
- if running the festos off of a pneumatics bumper look at the diagnostic lights to see if they are firing when told so. or even if the lights are on
- if they are 24v festos then make sure your bumper has 24v
I know I am missing a bunch of other common causes but im sure others will chime in.