Faculty sometimes need more time for getting their courses ready in Canvas. If that's the case for a course you're registered for, you will not see it on your dashboard when you log in to Canvas. You can check to confirm that is the case by clicking "Courses" → "All Courses" as seen in the following screenshot:
On the "All Courses" page, you will see a list of all the courses you are enrolled in currently. Look for the course(s) that do(es) not appear on your dashboard, and under the "Published" column, see if it says "Yes" or "No." If it says "No," that means your professor has not published the course yet. You can either wait until it is published or email your professor to ask for whatever course material you may be seeking in advance.
Another reason you may not be seeing your course is if it doesn't have the star checked on for it. In the above screenshot, you can see that the courses under "Past Enrollments" don't have the star checked on whereas the courses above the "Past Enrollments" do. Click on the star next to the course you want to see on your Dashboard when you log in to Canvas.
If you need further assistance, click the "Help" icon located at the bottom left of your Canvas window or email firstname.lastname@example.org.