I bought some RWS cases and could not insert them into my Lee shellholder, bought RCBS shellholder, same.
Turns out that RWS did not cut the extractor groove deep enough on their cases.
Used a small grinding wheel to open up the shellholder.
Problem solved.
There are several Redding dealers in Canada. Why not return it to the Redding dealer you bought it from?
I warrant all product I sell I am sure that the dealer you bought it from will do the same..