QXp 10 Help Topics menu option failure in Yosemite

[PrintersDevil]

Can anyone suggest why I am having no luck in accessing the Help pages which I assumed were loaded in full in Applications>QuarkXpress 10
Is there a particular reason for the Quark help topics menu option no longer working? I used to have to give it two goes before it opened but now it will not stay open.
The index page appears for a few seconds and a topic can be clicked to before reverting to "The selected topic is currently unavailable."

I have tried downloading the QXP Help.app software again but maybe this 2013 version is no longer compatible.
I are sticking with Yosemite !0.10.5 on our iMac (late 2012 model) for fear of making other required software un-useable.

Thanks for any guidance with this.