Line 474 of the External Database enrollment type has incorrect logic when determining whether to build courses.

if (!$this->get_config('dbtype') or !$this->get_config('dbhost') or $this->get_config('newcoursetable') or $this->get_config('newcoursefullname') or $this->get_config('newcourseshortname'))

{ return; }

should be:
if (!$this->get_config('dbtype') or !$this->get_config('dbhost') or !$this->get_config('newcoursetable') or !$this->get_config('newcoursefullname') or !$this->get_config('newcourseshortname')) { return; }

As it stands now, if those fields AREN'T empty, it will skip building courses, and do nothing. If they ARE empty, it will try to build the course, but fail because those fields are empty.