If you cannot access Google Drive assignments or files in Schoology, you may need to remove / revoke Schoology access to your Google Drive and then re-add it.
How to Revoke Schoology App Access
Select Security in the left sidebar.
Select Third-party apps with account access.
Click on Schoology. Then click the REMOVE ACCESS button.
Note: You may notice Schoology listed in both the Third-party apps with account access section (Schoology) and Signing in with Google section (Schoology and Schoology Integration). If removing access from the account section doesn't fix the issue, then you may also need to remove its access from the Google sign-in section as well.
After removing access, in Schoology under Resources >> Apps, you will notice the Drive is no longer connected.
Click on the Google Drive Resource App to reconnect it.
If this does not resolve the problem, then follow additional steps for reconnecting the Google Drive Resource App in Schoology.