I have been moderating Moodle for a few years now and have never encountered this problem. I recently just created a new course and have Manually Enrolled users. For some reason these users cannot see the course. I have never had this problem in the past. I've tried to unenroll and enroll over and over, still no luck.
I usually copy a previous course and just update. I have never had this issue. I would greatly appreciate any advice since I have not messed with any settings.