Piston Won't work.

Ok, so I have a Sticky Piston connected to redstone that is connected to a lever. The piston also has a block on it that I need it to push and retract. When I flip the lever and the redstone is activated, the piston won't push. When I destroy the block from the piston and then flip the lever it works. Why won't it push that block or retract it? My Minecraft Version is 1.12.2