Place an Element.Parameters node and make sure there is a parameter with exactly that spelling (capitalization matters) for each element you selected.
To clarify: place the node after the List.UniqueItems node.
Sorry for my late reply.
I don’t understand what you mean placing
can you show how?
Thanks
Wire the watch node into it. Then preview the results at index 0 (a[0];).
Sorry for my silence, I’ll resume the exercise ASAP 
hello friends i have a question that complicates me
to solve the problem myself
I work with REVIT 2020.2 end DYNAMO revit 2.3.0.6270
I used a parking census scheme with revit 2017 with dynamo 1.2.1
after updating the mode with the new versions DYNAMO revit 2.3.0.6270 the scheme does not work please help me fix it so it works smoothly
thanks in advance
What part of it didn’t work?
Element.set.parameterByName
just this 
Look I see have null after in previous version 2017 revit ,dynamo worck’s good
In this place a have null something cont gat to Understand With ones of command not properly working I think wit Nuw version on dynamo and revit 2020.2…some one knows how to fixed
Place 
What do you have for the prior node?
Change your parameter name “Mark” to the france name of mark (Marque ?)
You’re warning says that the parameter doesn’t exist.
Maybe that’s the problem
Hi I try
What are your mind “… name “Mark” to the france name of mark (Marque ?)…”
can you explain me a little more accurately Place
Hi
I will check and show the nodes
hi
this is what happens after I try to number parking lots
does not accept a parameter and zeros begin
can you please help me how to number the parking lot
Are there any ‘true’ values in the bounding box intersection test?
Might be the bounding box of the parking stall not being tall enough to catch the points. Try adding an extruded line at a corner of the stall, controlling it’s height by an instance parameter. Give it a 1” height and see if that catches any points. Alternatively you could try and make lines at each point along the curve but that will be much more difficult computationally.
I also recommend you move on from list mapping and use list levels instead. Far easier to manage and decipher the errors.
Hi
this is an interesting point of view i will try with extruded
and what size to use for the expander can you show me the node and where to connect it
hello
i tried but it doesn’t work
something with the commands because at revit 2017 works perfectly
please help