A knowledge base article about How do I de-link my Google account from bCourses? provided by the UC Berkeley IT Service Hub - Knowledge Portal
When you connect your Google account to your bCourses account (which is usually done when instructors use the Collaborations tool for sharing Google Docs, and/or so that students can upload files from their Google Drive), you must be logged in using your bConnected (@berkeley.edu) account.
If you are logged into Google with your personal account, then the connection to bCourses will not work.
To fix this, follow these steps: