Your integration with Canvas™ requires you to open each assignment from Canvas before you can open it from your home page in WebAssign.
Resolution
Open the assignment first from Canvas.
Opening the assignment first from Canvas allows the assignment score to sync to the correct Canvas activity.
If doing so shows the same message again, notify your instructor.
A specific error in setting up the integration between WebAssign and Canvas can cause this problem. Your instructor can fix this by following instructions in the instructor help.