It might be possible on some scenarios that Subpages are not being shown as expected. Some Subpages or all of them are missing on some views.
Release: Component: ODPRD
Sometimes the PPM administrators configure display conditions of type (1=2) on subpages that they don’t want to appear anymore. They would normally do that for testing purposes or to keep old versions of subpages that might need in the future. This can cause problems and unexpected results on other display conditions on other subpages on the same view.
If the display conditions are not working fine on a given view (for instance, Program Properties), make sure that no display condition of type “1=2” is configured on any of its Subpages.
In Studio, go to problematic view (f.i, for the Program Properties Edit View)
On the Project Object, select the Views tab.
Click on the Program Properties View ([Layout:Edit] Setup)
Object: Project | Partition: System | View: Program Properties | Mode: Edit - Property Layout
For each Subpage, click on Properties and Layout.
Double check its configure Display Condition.
If a condition of type “1=2” is found, reconfigure it to something that is supported, but that would not be met either. For instance, something like (Project Name = "This Subpage will never be displayed")