I have had a similar issue, but it turned out that something had caused the
Enable ... box to go blank. So I had to reset it and save, and then it worked again.
Obviously, yours has not gone blank, so what I'd suggest is that you install the WP Crontrol plugin and then check the list of Cron Events it finds (under
Tools->Cron Events in the WP admin menu). You should see one there listed as
If it appears there, then it should be working.
If it isn't there, then I suggest that you reset the Auto EOT behavior in s2Member by making the first box blank, saving, and then setting it to the right option and saving again. Then check that the Cron Event appears in the list as it should.