Sometimes you will need to post a reply in order to see other replies in a Discussion.
Open Discussions
Click the Discussions link on the Course Navigation.
Open Discussion
Click the title of the discussion.
Replies Visible Option
Click the check box Users must post before seeing replies option.
View Discussion
If you cannot see the other responses, make sure you have posted to the Discussion. You will see "Replies are only visible to those who have posted at least one reply." Post a reply to the Discussion to view the other posts.