RelationInfo function not working in my file

[Tom R.]

Hi, 

I'm trying to implement NightWing's Duplicate Hierarchy v2 technique in my solution. The file (my solution ) has been in use for years, but does not appear to be corrupt. But the technique relies on the RelationInfo function, and it does not appear to work at all in my file, although it does in other files. 

Any clue as to what could cause this? I've taken screen shots of the Monitor window showing that it is passing correct parameters, and part of the graph showing the table & its relations. 

Thanks for any help!