When using MATLAB Grader in an LMS (i.e. LTI integration), due dates are not passed to MATLAB Grader, and therefore have no impact on its behavior. If the LMS allows students to still access the problem, then they will be able to launch it. You need to use your LMS settings to make the problem not visible to your learners if you no longer want them to be able to launch the problem.
Typically, setting a due date in an LMS only impacts how the grade is reported to the gradebook, not visibility of the problem. And even then, you will want to verify what your LMS' behavior is with due dates. It may not do anything.
