Did this just happen to you?

If so, it's probably because you have another GSuite account and you are logged in to the web browser. In fact, if you look at the bottom of that error page, it will show what account is active. [In the image, it's the bubble that says "NOT YOUR SLU ID@gmail.com.] If it's anything other than your SLU login (something@slu.edu), you cannot open the file.

The most direct solution is to click on that account name; a new login window will open up, allowing you enter your SLU login.

Alternately, you can change the login in your browser. Contact me for instructions, if you need them.