We have seen two issues crop up occasionally that are both actually easy to fix:
1. You inadvertently inserted a space before or after the CRN in the "CRN" field in your Moodle course settings area:
That one is easy to fix by making sure only the five digits are in the field. Shortly after you fix it, your students should be auto-enrolled.
2. You haven't run that Moodle course shell since we transitioned to Moodle 2 in June 2103. This one is a little trickier to identify, but still well within your ability to diagnose and solve it.
First, click on "Enrolment methods"(we know; it's the British spelling) under "Users" in your course Settings block:
Next, look to see if the eyeball is closed for "Conduit" (that's the name of our auto-enroll tool that talks between Banner and Moodle). If it's closed, click to open it:
That should wake up the auto-enrollment method, and give your students instant access to your Moodle course shell!
Of course, if neither of these solutions work, let us know. It may be that you accidentally input the wrong CRN into the CRN form, and/or (worse yet) the Multiple CRN Enrollment form - but that's set of issues altogether…