Came across a problem where this plugin would not work for a drawing. It would try import the text from a dxf file but no text would appear in the SU model.
The ruby console showed an error "VALIDITY CHECK = Txt - invalid group".
I narrowed it down to a few Text entities which had "%%C" symbols in their text content (the diameter symbol in AutoCAD).
I changed them from "150mm%%C" to "150mm" and the import worked. Just one text with the %% means nothing in the drawing imports.
Just said I would post it here in case anyone else has this issue.