Procedural mesh, change value of vertices don't change mesh in the scene

I’m trying to work on this project, but unfortunately, I’m stuck. My idea would be to modify the appearance of a mesh at runtime using procedural mesh. Right now, for example, the idea would be that for this mesh, all its vertices with z < 40 would be modified as in the blueprint. It’s not the final result I want to achieve, although it may be a vague idea, but I only needed it as an example. Because in fact, I’m stuck even before making the correct deformation, that is, when I run it, no changes occur. Does anyone have any ideas?
I need to change approach?

  • The print is used for debugging, and I confirm that it prints many vertices with z < 40 on the screen.
  • Before the first visible node, there is only the On Tick node, plus a quick system that ensures that we reach the first visible node here only once every 10 seconds

EDIT

  • One possible error is that the Copy Procedural … node is to put afer a Event Begin Play, and not in that position… yes? no?