Displacement doesn't work

hi guys, i’m trying to create a new material but i can’t understand why displacement doesn’t work. as you can see in the attached photo. can you help me?

Make group with this geometry and apply material directly on group.

ok, if I do it on a plane I can assign the material to the group and the diss works. But in this case (of the chairs) I can’t assign the material to the group. what should I do??

Try to assign inside group and outside group same material. It should work.

PS. I think this is not best solution for such effect. Try to make normal bump of this texture. https://cpetry.github.io/NormalMap-Online/

It should be enough for material of chair.