When you say they aren't working do you mean that they pop-up but don't spray, or that they don't pop up.
The water pressure is what pops them up, so worth checking if you have a leak in the system (puddle under the car should be obvious). Also possible that if they haven't been used in ages then they have just got gummed up with road grime. You can prise them up out of the bumper with your fingernails and check they operate freely.
Seem to remember that you are supposed to use a certain washer fluid as well as the pipes are quite narrow and so can get gummed up with residue.