If you use Time Machine to backup your Mac to an external hard drive, here are some basics that you can check if backups are no longer occurring. I’ve written many tech tips about the importance of backing up your Mac, including one about setting up and monitoring Time Machine. If you ever notice that Time Machine is not backing up your Mac, it’s typically easy to get it working again. The most common problem is that your Mac has either physically lost its connection to the external hard drive or the Mac is confused and unable to communicate with the external hard drive.

Here’s how you can troubleshoot this situation:

Go to the Apple menu and select Shutdown. Wait for your Mac to turn itself off.

• Locate the cable that connects your external hard drive to your Mac.
• Disconnect this cable from the back of your Mac.
• Then locate the on/off switch on the hard drive, if it has one, and turn it off. Then turn it back on. If the drive doesn’t have an on/off switch then it might have a power cord which you could unplug and then re-plug. (Some drives won’t have either a switch or a power cord. They get all of their electrical power via the cable that connects the drive to the Mac.)
• Reconnect the cable to reconnect the hard drive to your Mac.
• Turn on your Mac and wait for it to startup.
• See if your external hard drive’s icon appears on the Desktop and/or in the left-hand Sidebar of a Finder window.
• Click on the Time Machine icon at the top of your screen, near the clock and select Back Up Now.

Wait a few minutes for a backup to occur. Click on the Time Machine icon again and verify that it lists the most recent backup as occurring today.