This post is to help others with this vexing problem, and yes , it is totally my fault / operatop error.
But now I am happy.
I recently created a very large project in Encore with 14 15 minute clips in Encore.
Besides using a Playlist to play all, I also created several sub Menus and to make navigation
easy in BluRay I created a popup Menu.
IT DID NOT WORK despite me checking links to the timelines and setting the menu as a popup.
As I am working in PAL, I am limited to 1280 X 720 res at 50 fps. for BluRay stuff.
All my work is shot in 1920 X 1080 at 50 fps.
Alas, I had created the Popup Menu in Photoshop with the res of 1920 X 1080.
It did not work., but after a lots of investigation and when I reduced the menu to
1280 X 720 it worked.
A valuable lesson.
Hope this helps others.