@Hyunu_Kim I can reproduce your issue in Revit 2019 using your file.
The issue is that this PR:
started serializing dropdowns using a new enum, that enum does not exist in old versions of dynamo, and very old versions of Dynamo 2.x don’t handle this case well, so the whole graph fails to deserialize.
I am not yet sure the range of versions newer than 2.0.4 - but those before this PR went in which are affected by this change.
The bad news, theres no great way to retroactively fix the old version of Dynamo.
the good news is your files can be converted to load in both versions - just find and replace the string “dropdownSelection” and “hostSelection” with “Selection” - and the file will open.
we are investigating solutions.