Google OAuth Invalid Grant Error
From CompanionLink Support
Syncing via Google uses OAuth to authenticate.
The invalid_grant error message indicates that Google has expired your OAuth token. This happens occasionally. Google tokens generally last a few months or less, and then expire.
To renew it:
1. Open CompanionLink and go to Settings, then click the small Settings button on the right side (where Google is selected)
2. Click Request New OAuth Token (Or uncheck then recheck the Use OAuth For Login box) and follow the prompts
3. Sync
Your data will be preserved in this process. Until you renew, CompanionLink cannot synchronize to Google.