Why does the page tree view no longer display for existing spaces?

[victoria_hansen]

In the last couple of weeks, the Tree view (Default) for Pages no longer appears for existing spaces.  

The tree view has disappeared entirely for a couple of spaces and on one space it only shows one page and its sub pages.  

However, for newly created spaces the tree view is present.  

NO Tree in this existing space: 

Only partial tree present in this space:  There are plenty more pages and pages with subpages that should be appear. 

[Deepak Jain]

It looks as if you gave moved the home page of the space.

Can you please check, if there is the correct home page set in the space detail settings? This should be a tab next to the orphaned pages.

Try to set a new home page to fix the problem.