NOTE:
There are two time configurations that will play a big role in using the Application Portal which are to be maintained every time you open a Course for application/enrolment, see System > Edit Time Period for more details.
UNIT_ENROLMENT – it controls the scheduled units the student can enrol from the Course Plan
ENROLMENT_PERIOD – period that opens or closes the Course Plan to students [opens and closes online enrolments for students].