Assigning Parameters to All Elements in a Category Excel Import Export

I apologize if this question has an easy answer but I am pulling my hair out trying to write parameters from an excel file back into elements in a Revit file. I am trying to make sure that they get written to the correct element by using the UniqueId (as suggested by http://bimtroublemaker.blogspot.co.uk/2014/09/practical-dynamo-excel-linking-2.html & http://www.revit.com.au/?p=1564) I seem to be able to export the data to excel fine, but trying to bring that data back in is causing me issues. I would eventually like to allow for the architect or whoever is viewing the excel document to be able to change room names and the element name, but I am still a beginner at this and have no idea how to do that. I am getting errors when setting parameters in the categories “Product Description”, and Dims 1, 2, and 3 (probably due to some null values) but the lists created in the GetItematIndex Nodes are not the same as the SetParamaterbyName node and I can’t figure out the issue as I followed the instructions in the two links above as well as a plethora of other pages in these forums.

(edit: The code block is throwing this error: “Warning: ElementSelector.ByUniqueId operation failed.
Could not obtain element from the current document! The unique id may not be valid”)

The difference I noticed was that they did it using the families as a starting point instead of categories but I can’t see why that would make a difference. Any help would be greatly appreciated and I’ll do my best to help on the forums once I gain some competency in it.

Thanks in advance