This is going to sound really dumb.. but I have found that even if the classifications match but were created separately (i.e. Make the Classifications on Suite A, then make the same classifications on Suite B) then this fails...
In my experience they need to be made at the same time with both/all suites selected... so that the classifications are applied to all suites simultaneously... I suspect there is some sort of classification id (behind the visible names) that is created in the system, and those IDs have to match for this to work.
When I had this issue in the past, I had to delete all the classifications from all suites individually, then select all the suites, then re-create the classifications....
Because I don't want to risk having to re-do work, I have always created classifications with all suites selected for a few years now (just in case this was still an issue).
