I have one of those Vidi 24RT digitisers.
No interface means it cannot detect the Digitizer on the parallel port
Here you can see what was in the box when you bought one:
http://www.amiga.org/gallery/index.php?n=1214Note all the stuff is labelled 24, there are no items labelled 12 (at least for me that was the case)
I wonder if you have the wrong software and that's why it doesn't recognise?