You cannot change any grades for a student that has a concluded enrollment. All students’ Sem 1 enrollments were concluded the first day of the 2nd semester.

How to Restore a student’s enrollment:

Go to the Course

Select People

Click the Gear icon in the top right

Select View Prior Enrollments

Click student’s Name

Click More User Details…

Click Restore this Enrollment

If you change a grade within Canvas after grades have been exported into Infinite Campus, then you must give the student's new Final Grade to the office manually.