Issue:
When courses are created for an upcoming semester, the current semester's courses may be pushed from the dashboard if the total course number for the user is over 20.
Solution:
Canvas regulates the number of courses presented on the dashboard to a maximum of 20, but you can locate missing courses under "Courses > All Courses".
When no courses are favorited, the courses list automatically displays up to 20 courses alphabetically in the drop-down menu.
However, once you have selected at least one course as a favorite, only your favorite courses will appear in the Courses list.
Please review this article about Customizing my Courses List for more information.