In Revit, Rebar needs a structural element to host it, such as a Structural Column or Structural Framing (beam) that also has a material for model behavior (not the normal material) that allows it to host such as concrete or precast. Also, floors (slabs) and foundation elements can host rebar.
It appears from your graph that you are passing the detail line into the “Host Element ID” input. Detail lines cannot host rebar.
Joe