Try running the script in a new project created using “Template = None” and using one of the columns from the library that installs with Revit (clean Revit file with clean (ish) families). You’ll need to just create a few levels then load the column family. If it does not work in that case, then there is perhaps an issue with your script (does it exactly match Vikram’s?). Once you confirm that it works in that case, then try loading your column family into the clean project and try again. If it still works, then have a look at your firm’s Revit Template in the Manage-Project Parameters area for parameters that might be duplicates of some other built-in Revit parameters.
As you get deeper into Dynamo, you’ll be doing a lot of Element.SetParameterValueByName, so you will likely want to clean out all of those duplicates and make all of you parameter names unique. There are ways to specify which parameter you want if you have duplicate named parameters, but that’s going to involve some more in depth python-ing and some digging into parameter GUIDS, etc.