I've got the same problem as described in this forum post: https://moodle.org/mod/forum/discuss.php?d=219400
On the enrolment options screen, the 'Enrol me in this course' link in the admin block isn't working but the 'Enrol now' button under the course description is.
The link in the admin block appears to link to the same page, leaving the user unenrolled on the course.
There doesn't seem to be an answer in the forum post above so I'm wondering if anyone has since had this problem and found a solution.
Please let me know if you have.
I'm using Moodle 2.6.2; I've got self-enrolment enabled and no guest access allowed. I'm testing it as a newly enrolled authenticated user.