By default, Canvas courses are not automatically published at the beginning of the term. This feature gives instructors the opportunity to fine-tune their courses before making them available to students. Instructors must publish their courses before students can access them.
The course status can be found on the right sidebar of the home screen (see below). Courses can be published and unpublished using the "Publish" button. Once an instructor has graded any student work, the course can no longer be unpublished, and the course status buttons will disappear.
Please note that you cannot send messages to your class through Canvas until your course is published.