Hi Joseph
I just see this post, I think you may find good solution already.
Anyway, I add my recommended here for someone who may have same problem.
This come from difference model version, later the model use more specific item type for their input data.
Actually the way to solve the problem is to open dfs2 file that M21 complain about it item then change Item Type (meny edit/item..) to what M21 model required.
Regards,
Somchai.