When I Translate a page in Episerver 9 the Display in navigation check box is greyed out. Is there a reason for this?
"Display in navigation" is not culture specific property, so you can edit it only in master language.
If you need this to be culture-specific, it's easier to add another culture-specific property, called ex. Display in listings or Display in menus and use that one.
There is a long discussion if it's possible to change this property to be culture specific here: http://world.episerver.com/forum/developer-forum/EPiServer-7-CMS/Thread-Container/2014/1/Override-built-in-page--block-properties/