Error: auth/email-already-in-use

This error usually occurs when the GitHub account that you use to set up the sync is already associated with a different GitBook user account.

Error: auth/email-already-in-use
Firebase: The email address is already in use by another account. (auth/email-already-in-use).

How to identify which GitBook account is linked to the GitHub account:

1. Log out from your current GitBook user session (i.e. [e-mail])

2. Log out from any GitHub user sessions.

3. Go to the login page.

4. Select the "Sign in with GitHub" option.

5. Enter your GitHub credentials.

6. Once logged in, go to the account settings and either:

   1. Unlink the account from the "Third-party Login > GitHub" section in the Personal setting

   2. Delete the account altogether if you do not need it.

7. Log out from the session.

8. Log back in using your [e-mail] GitBook account.

9. Try to set up Git Sync again.