Check settings - if "Block third party cookies" is enabled. Disable it.
Make sure the student is not logged into any other Google account.
If those solutions don't work:
Have the Student visit this URL: https://lti-submission-google.app.schoology.com/authorize/logout when trying to view the document, then have them re-connect their account. Make sure the Student is logged into the correct account in their browser before trying to re-connect the account
Get rid of unneeded extensions.