The permission check at myportal/control/FindPortalPage always fails due to missing permission PORTALPAGE_MAINT that has no demo data.
If PORTALPAGE_MAINT should remain the permission to be checked then demo data needs to be created for it.
PORTALPAGE_ADMIN is the only PORTALPAGE_ type permission that exists if PORTALPAGE_MAINT needs to be replaced. However the menu to access the page in the first place uses permission MYPORTALBASE_ADMIN for controlling the display of the link.
Whatever permission is chosen needs to be consistent with the menu link.