If you have users who are not showing up on the leaderboards, it's most likely because they never set their gender when they first created their account on your site. Their are 2 ways to fix this: the user can edit their profile and select gender, or you can edit the user from Admin > Settings > Users > Edit User.
The user should be prompted to update their information (including gender) each time they login to your site from when they create their account until they actually do update their information. You can require your users to update their information at anytime by checking the box on the edit user screen.
The other reason might be the user has turned off sharing their log with the team. Users can choose which team sites have access to their log. Users can change this setting in their user profile.