Why can't some of my customers access our linked confluence sites?

Question

I have customers how can see all their support requests in the Service desk but they can not see the linked confluence pages.  
All they get is "No access, you do not have permission to view this confluence article"

We do have "Any active user can view this space" permission in the confluence site.

Kris Dewachter · Answer

@Patrick Gallagher ,

It's strange that they can see the titles, but not the individual pages. I was thinking about individual page permissions, but in that case they would also not be able to view the page titles.

Patrick Gallagher_v8aoco · Answer

I would also add they can navigate around the knowledge base and see all the titles, just they have no access to the individual pages

Patrick Gallagher_v8aoco · Answer

It looks like it should be ok to me.  
Who can view = All logged-in users
Who can edit = Only Confluence users