Take a sceenshot of the material and attach it to the post.
If the entire mesh moves than I am guessing you either plugged the math into the WPO node vs WorldDisplacement, or you have something like a flat-white texture as the map? A pic is 1000 words, get one
I see your tessellation multiplier at 0, it needs to be a positive integer. Also your heightmap seems to be almost a solid color, so you wouldnāt expect to see much relative displacement. Try it with the cobblestone textures I had in my screenshot to see if it works at all in a material, or itās something else in your settings.
In regards to not moving the mesh, you are using a map to adjust the physical positions of the mesh-vertices; itās expected to move somewhat. Larger values will move it more.