If you are having issues with Time Machine backups, learn how to troubleshoot them. These tips can help if you have previously been able to back up via Time Machine.If Time Machine is unable to complete a backup, make note of any alert message that appears. You can also click the red "i" icon next to the word "Failed" in Time Machine preferences (in System Preferences) for more information. The tips in this article relate to specific alert messages and situations.