Some of your Strava data may be showing up in the NBC, and some not. Sometimes, the data Strava send to the NBC gets lost on the way through the aether. As long as your data is in Strava, the Sport is "Ride" and the "Trainer" tag is not checked, it will show up in the NBC. Sometimes this happens instantly, sometimes upto fours later, and in really bad cases, on Saturday an audit script runs to clean everything up.
There is also the first of the month panic. Until you log your first ride of the month, you won't show up on the leaderboard.