It can come down to several factors:
Track Set-up
Make sure the track is set-up appropriately. Private vs Public track, etc.
Membership Set-up
When creating a membership, make sure the tracks you wish to give access to this membership are selected.
Class Set-up
When creating a class, choose the appropriate track for that class.
If you set all three up appropriately, your members who have the appropriate memberships will be able to see the classes they have access to based on their membership.
If you're still having issues, email support@chalkitpro.com so we can look into the issue further.