Probably the reason is lack of permissions to columns, which most likely could have been added or edited by the administrator.
How can I fix it?
Just go to the Secretariat and Settings tab and then select the System configuration tab and enable the „Teachers share the grades in groups” option. Save changes, log out and log in again.
Ask the teacher to log back into the system. He will now be able to enter the grades even if the column has been added by another user