How can I troubleshoot a '403 Error' when trying to access a Google service like Google Drive?

Troubleshooting involves several steps. First, verify you're logged into the correct Google account. Second, check if the file or folder has been shared with you, and if so, check the sharing permissions. Third, clear your browser's cache and cookies. Fourth, try accessing the Google service in a private/incognito window. Fifth, check if your Google account has any billing issues that might restrict access. Finally, contact Google support if the problem persists.