Firstly i have posted a bug report about this here earlier in the year, but there has been no updates so though i would also push the issue here, see if others had the same issue.
So my issue/ the bug is Element.SetParameterByName fails on setting subcategory for solids. The current logic works with ModelCurve.ByCurve and also ImportInstance.ByGeometries , but not with freeform solids created by Spring.Form.ByGeometry Import instance is not an option.
Attached is a slightly updated code for those interested in the issue or ideas on work around while we wait for the bug to be fixed.
Revit:
BUG-Element SetParameterByName-Solids.rfa (320 KB)
Dynamo:
BUG-Element SetParameterByName-Solids.dyn (64.2 KB)