In Enterprise Course Planner, students are not directly associated with activities. Student sets are allocated to activities, and students are allocated to student sets.
A unallocated student is associated with a module, but is not allocated to a student set for the activities of that module. This situation might occur when a student has been allowed to make a selection of modules that was not planned for, or has changed their module choice since allocation.
You can rectify this situation by allocating the student to an existing student set. If no student set that is allocated to the correct modules exists, you might need to create a new set to accommodate the student.