When you delete a CommonLit assignment on Canvas, that does not delete the assignment on CommonLit. As a result, you may receive an error that the assignment is already assigned because it still exists in CommonLit.
If you would like to re-link the CommonLit assignment to Canvas, go to your class's Assignments page and click the Dashboard button.
On your Assignment Dashboard Page, click the Unlink Canvas button.
Once you've unlinked the assignment, you will be able to re-link it on Canvas.
Alternatively, if you would like to reassign a brand new assignment, go to your class's Assignments page. Then, click the trash can icon in the top right of your assignment to delete it. Once you've deleted the assignment, you will be able to reassign it to your class.