Hello, I am trying to create 100% hidden stairs (as long as they are along the wall), and i have it pretty much done, except that sometimes the pistons won't extend when they are powered, the power is coming from right underneath it.
Can you post pictures?
Do you use torches or powered blocks beneath the pistons?
If torch, do they change or is it possible that they burned out?
If block, did you made sure that you have a straight redstoneline into it or repeaters?
Sorry if this sounds dumb, but without pictures i can only propose a few common problems.