WPLMS creates membership for Every course. Users joining a course get subscribed to course membership.
a. Every course have maximum duration setting. This duration is the maximum allotted time under which the student must complete the course. When this time expires, the student sees, "course expired" or lesson expired in this case.
b. A Course can be sold on subscription basis via product, points. This subscription overwrites the course maximum duration. So when the subscription duration expires for the course-student the "course expired" status appear.
To remove this, simply click on the course expired button, if the course is connected to a product, the user can again purchase the product to extend the subscription duration.
Alternatively, she can request the instructor and instructor can increase subscription duration from Course - Admin settings :
https://www.youtube.com/watch?v=2WEGP_8mGn4