I am using Moodle 3.3.3 .
Latest announcement block (on right side) on the course page is not visible. It is visible in subjects of earlier semesters along with SEARCH FORUMS, UPCOMING EVENTS, RECENT ACTIVITY.
I have checked in Site administration>Plugins>Blocks>Manage Blocks, it is not hidden.
This semester I did enrollments via External database, till last sem I did enrollments with running cron job. Hope this might help.