Individual Parts not Playing Back in Vertical View

Good day,
My master score plays but the individual parts are not playing. I have even uninstall and re-installed but it makes no difference. I know I can get it to play in horizontal mode by clicking and ensuring I see the blue color but when you are teaching kids and you want them to see in vertical view as they would see their sheet music and you are not getting same it defeats the purpose.

Anyone knows how to solve this?