What you are seeing
A padlocked note above the grid: "The report cards for this term are released, so its attendance is closed. Take the release back if a day is wrong." Every cell in the term's months is read-only, and Mark everyone present is refused too.
A learner is already holding a card with those totals printed on it. Changing the register underneath them would leave two different truths with no explanation, so the term closes instead.
Correcting a day anyway
- Class → Release → Take back the release. You can give a reason; it is shown to you only.
- Go back to Attendance, pick the month, and open the week from its dates in the header if it is locked.
- Fix the day. The term totals recompute as you mark.
- Release the term again. The new cards carry a revision number, so nobody is left comparing two cards that look identical.
Taking back a release stops the old one-time links working, and the delivery checklist starts again for that term. It is worth being sure the correction is the one you want before you begin.
Only that term is closed
Months belonging to a term you have not released stay fully editable. If your class runs three terms and only Term 1 is out, Term 2's months carry on as normal.
If Release is not available to you
Releasing belongs to the class adviser, and a subject teacher in the class can view the register but not mark it. Ask the adviser to take the release back and make the correction.