Within CBSubs > Subscription you need to find the users subscription. Once you've done so you need to click the id in the ID column to the very far right. This will open the users subscription allowing you to see and edit details of their subscription. There you'll find "Expiration date:" to see exactly when the user is supposed to expire. If they've surpassed this date then in "Status:" set them as "Expired" and click "Save". I've no idea why some of your users aren't expired.

My only guess is you had the plan with a longer duration or grace period then changed it after they subscribed. Another possibility is you don't have a way of triggering expiration properly. You can configure expiration triggering within CBSubs > Settings > Global > Automation settings.