This happened to us when we were trying to get Canvas LMS buy-in from our instructors and not working created a hurdle. And now, the Office 365 Cloud Assignment portion of the Office 365 LTI is not working again. The Office 365 file attachment is working fine. We have submitted a support ticket asking for advice on who we need to contact, but to date nothing but the standard "we received your request" response from Canvas. If you have experienced this problem and figured out how to resolve it, please reply. Thank you.