I am trying to build a piston door, but I have ran into a very odd problem that I have never experienced before. Well, I will just let these screenshots show it.
See here how the piston acts normally, extending with the redstone torch.
However once I put a block in front of it, you know, so it can push it, this happens:
The piston will not extend. I placed the piston on a different block, to the left of the torch, and it works fine. But if I put it on that specific block, it stops working. All three of the other pistons on the door is working just fine. there is no other redstone in the within two blocks of it, and even when I did remove the other redstone, the problem persists.
Are there any other pistons that work in the immediate area?
I see from your screenshots that you are in a faction world, most likely only those in the faction can edit the terrain.
The problem might lie in the fact that the piston is trying to update the terrain by moving and overwriting blocks, which the server is denying.
A reason that it could work with out the block is because the piston is just writing in block data into that space, and not overwriting.
Solution: Unclaim that land, or contact server admins with the problem?
Workaround: Try moving the pistons in 1 block closer, so the arms of the pistons block the door way. It won't be much for camouflage, but a) it will keep people out (if it is protected) and faction land is acknloged in chat anyway, so you it would have to be on the border for camouflage.