Eventually, I found a link on the community site, but it asks me for a password, because it’s a private course. I remember being able to find it before. Is it undergoing maintenance?
This typically occurs when a course is brought to its end of life, so to speak. Those who have previously paid for it will retain access but no additional students will be able to enroll.
No official announcement has been made yet but I suspect this is due to some housekeeping of courses.