I am getting new messages that my "backup" is not going through. You fixed it last time but not sure it is a problem.
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While time machine is a very good backup method, sometimes it needs a little love to get back on track. There are many things that could be causing your backup issue. No way of knowing what the actual cause is. Some possibilities are:

1. Drive needs to be reformatted and backup started over.
2. Backup drive has failed.
3. Your Mac may be wanting to back up to two separate drives and it hasn't seen one of them in more than thirty days.
4. Drive is not mounted. May need to be unplugged and reconnected.