Hi Erman,
When I make every project in Oaf R12.2.6
I use PageLayout Region as Top-Level on the page.
when the page's top level region is "pageLayout", the table does not contain any data.(no results data)
So when I do top-level region style to defaultDoubleColumn / defaultSingleColumn I get data in table.
This is a development-related issue.
Maybe you should not even select that problematic region.
Maybe the region and your development should be aligned to work together.
Jdeveloper logs may tell you something.. Any clues there?