We had a student encounter this issue and had to do a workaround to get her sorted out.
This student has Microsoft Office accounts from 2 different institutions (UCF and Valencia), which is fairly common. When she clicked on Submit Assignment and clicked on the Office 365 tab to find her file, she was logged in to her Valencia account instead of her UCF account.
As you can see in the attached screenshot, there is no "Logout" link on the page. (It's worth noting that there is a "Logout" link if the course has the Office 365 LTI enabled, but that does not help students whose courses don't have the LTI enabled.)
We tried to have the student directly log out of her Valencia Microsoft Office 365 account and then try again, but she was not prompted to log in again and was just taken directly into her Valencia Microsoft Office 365 account. We also tried clearing her cache in an attempt to get a login prompt but that didn't work either.
What we ended up doing was setting up a the Office 365 LTI in a development course and enrolling the student in it. This allowed her to take the steps in the following guide to log in to her UCF Microsoft Office 365 account: https://community.canvaslms.com/docs/DOC-10601-4212717403