Hello LisaMarshall1,
Are your trackers linked to rosters by your SIS? Or do you manually load your students? I would try reaching out to the person in charge of your Student Information System if it is linked with Mastery Connect. Otherwise, you can manually add them back to your tracker and their information should show in the tracker.
How do I manually add students to an existing tracker?
If you need to transfer students from a different tracker, please use these directions to do so. How Do I Transfer Students to a Different Classroom Tracker.
You can find more information about Trackers here: Create and Edit Trackers
Hope that helps!