The scenario is
1) The instructor sets date restrictions on assignments or quiz links. The link becomes unavailable or invisible to students after the due date passes.
2) The change in Blackboard is that if the student does not have a grade. after the link becomes unavailable to the student, the items disappear from the student's gradebook
3) Students who rely on the gradebook to monitor progress might not recognize that they missed an assignment. Blackboard uses a running total by default; the student only sees points earned over points attempted. If the instructor does not add a 0, the student sees an inflated average.
4) The student files a grade appeal because, in their view, they only see points earned over points attempted. The column is missing from the gradebook, and the possible points do not have the assignment/quizzes the student did not complete.
How to prevent this problem
1) Provide students with a list of assignments in the syllabus, so that the student has a reasonable way to know if they miss an assignment
2) Add 0s to the gradebook when the student missed work. You can add a comment to the assignment/quiz that explains to the student any options they have or that the instructor did not receive the assignment by the deadline.
Adding the 0s for missed assignments is a best practice even if the instructor does not set availability restrictions, as doing so allows students to see an accurate running total.
You can allow the student a late submission if desired. Just remove the 0 when the student submits.
A video that illustrates this issue.