Individual courses can have an end date different than the administration that it is assigned to. To extend the end date for a course use the following steps:
1) In the Administrations tab, open the administration that the course is assigned to
2) In the Course Sections table, search for the course
3) In the column marked "Evaluation End Date", click the 
button
4) From here, you will be able to adjust the end date of the evaluation accordingly.
Please Note: Extending a specific evaluation beyond the administration date will delay reports for all other courses in the administration.