TL;DR
Students need the correct identity and section memberships for their planner to show the right work.
Steps
Open Students in Insights and search by name or school email.
Open the student and verify the identifier, email and grade information.
Review section memberships and adjust them only with the required permission.
Save and inspect the student's current-year planner.
If memberships are imported or assigned automatically, correct the source or rule instead of repeatedly applying a local change. Moving a student between sections can change which teacher assignments they see. Do not create a second student record to solve a sign-in problem.
Related help
Why is Studyo asking for a school code? · Create and edit sections · Understand school synchronization