Apple: Time machine will no longer back up. Message says "backup disc is not in Mac OS extended format. What do I do?

A simple 6 step guide for solving this common Apple problem quickly and effectively by GetHuman

1
You need to reformat and erase the disk:
2
From the Finder pull down on the Go menu to Utilities.
This will open the Applications > Utilities folder.
Plug in the backup drive.
3
Click Disk Utility
> Click on the second left-justified icon (not "Macintosh HD").
> Parition
> Partition Layout > 1 Partition
> Options ... > GUID Partition Table > OK
> Format: Mac OS Extended (journaled)
> Name: Backup 1
> Apply
> File > Quit
4
Click System Preferences > Time Machine
> ON
5
Unlock the lock if it is locked
> Add or Remove Backup Disk…
Choose Backup 1
6
In the upper right of the menu bar:
Pull down Time Machine to Back Up Now

From then on when your Time Machine disk is plugged in, Time Machine will make hourly backups.
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Author: BenF • February 17th, 2016

About this Step by Step Guide

After thousands of Apple customers came to GetHuman in search of an answer to this problem, along with others, we decide it was high time to publish instructions. Here are just a few examples of the types of questions we were being asked or problems reported by users like you: Apple: Time machine will no longer back up. Message says "backup disc is not in Mac OS extended format. What do I do?; I have purchased ***gbytes of cloud storage, it's still in storage but Im being told I have *byte...; My iPad mini was stolen tonight when someone broke in my house; AppleCare returned my iPhone * without my SIM.; My phone isn't connecting to servers like servers for apple services like email.; I am unable to download an app but apple tries to send a code but doesn't recognize my apple id.... So we put together this guide to try to help. It has 6 step(s) to it. It takes an average of 105 minutes to get through these steps according to other users, including time spent working through each step and contacting Apple. And we tried to include a checklist of information you'll need when you try to fix this yourself. Best of luck and please let us know if you successfully resolve your issue with this.

Why does GetHuman Write How-to Guides for Apple Problems?

GetHuman has been working for over 10 years on sourcing information about big organizations like Apple that helps customers resolve customer service issues faster. We started with contact information and fastest ways to reach a human at big companies. Particularly ones with slow or complicated IVR or phone menu systems. From there, we realized that consumers still needed more detailed help solving the most common problems, so we expanded to this set of guides, which grows every day. If you have other problems or questions and you can't find the solution here, please let us know. We are writing new step by step guides every day for problems like this. And if you spot any issues with our Time machine will no longer back up. Message says "backup disc is not in Mac OS extended format. What do I do? guide, please let us know by sending us feedback. We want to be as helpful as possible. If you appreciated this guide, please share it with your favorite people. Our free information and tools is powered by you, the customer. The more people that use it, the better it gets.

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