I tried running the custom parameter node to the data port by itself and that worked, overwriting the information in the first column of my spreadsheet with all of the corresponding Space Type values (images 1 & 2). I then went back to running the default room parameters from LunchBox and that worked just fine (images 3 & 4). Finally I tried to run them again all together from the same List.Create node and the same error occurs at Excel.WriteToFile (image 5).
Could the problem exist between List.Transpose and the data port of Excel.WriteToFile? Is there a way to merge the two streams after List.Transpose? Also, if you look at the excel output in Image 2, you will see that some of the Space Type cells are blank, could these null values (or lack of values) be causing a problem? I did not get the chance to go through every room in the Revit model and apply a Space Type to every single one, I was hoping to do that after the definition was working properly.
@Marcel, unfortunately inserting File.FromPath between the File Path and Excel.WriteToFile nodes only generated an error.