If you receive an Error Code 424 when attempting to submit your work, it means you simply need to refresh your Google access tokens. Here’s how you do it!
1. Be sure you are logged into your Google account, and then click the following link to access the permissions section of your Google account: https://myaccount.google.com/permissions
2. Click on the GrammarFlip icon on this page, and then click the “Remove Access” button.
3. Go back to GrammarFlip login screen, click the “Log in with Google” button, and then follow the prompts to allow GrammarFlip to access your google account.