If the "Show all languages" option is disabled, it's because onyly one language is enabled on your site.
Go to admin > config > manage website languages and enable more than one language.
All the languages are already enabled in manage website languages section but still show all languages option is disabled.
for your information this is a migrated site from episerver5.2 to 6.0-->6.1 and then episerver7.0
See this blog post about how to enable this: http://www.dcaric.com/blog/episerver-7-5-how-to-enable-multiple-languages
Seems like you are effected by this known issue (#118502: Language Settings are grayed out in navigation pane when uiUrl is different than siteUrl in multsite environment)
which has been fixed and will be released sooon with Add-on update (7.1.8)
in Test environment Site, Edit mode --> Pages tab-->Show all languages option is disabled. but same is enabled in Development environment. Only diffrence is Dev is HTTP and Test HTTPS.