Hi Inhyeok, Thanks for getting in touch.

Courses created on the OpenLearning platform require an active subscription to remain online.

The course provider for the 3 courses you were enrolled in has chosen not to continue with an active subscription on our platform.

You could reach out to them directly to see if they have moved to another platform or find out their plans for the course. You could do this by sending them a direct message on their profile page if they have chat enabled.