When logged off Greek flag is not showing for the above pages. When logged in, the Greek flag shows at the header on those two pages.
Also, the parent page's grid view does not show those two Greek pages. The same applies either logged in or off.
Solution:
I checked the two mentioned pages; they were drafts, so I published them.
Please note that when using the "Yoast Duplicate Page" plugin, the cloned pages will be drafts in both languages, and you need to publish them separately.
