Could you clarify what "unable to use custom query" means?
The custom query is in red. (Simple one as "SELECT * FROM [Y & Y-1 Orders with Pyramids]")
If I try to recreate it, I got the error:
Database error 0x80004005: External table is not in the expected format.
; The query: SELECT TOP 1 * FROM ( SELECT * FROM [Y & Y-1 Orders with Pyramids] ) [Custom SQL Query]
Hmm, not sure if I ever tried connecting to a query.
Did this ever work for you before?
I'll have to ask around if this is supported :/