https://community.canvaslms.com/ideas/17382-catalog-enrollment-notification-to-teachers 

When a student enrolls in a Canvas course via Catalog, the only ways to tell are to look at Catalog reports if you're an admin, or check the course, if you're a teacher or admin.  We have a number of self-paced courses with continuous enrollment in our Catalog, so enrollments can be sporadic. We'd like teachers and admins to get an email notification when someone has enrolled.  That way we are aware and can check the student's progress.

Thanks,

Joan