Can't mount external hard drive mac, how to fix it and recover lost data?

Updated by Tim to Mac Data Recovery on March 27th, 2020

Since updating to macOS Catalina, my Seagate 3TB external hard drive is not mounted on Mac. In Disk Utility I cannot do anything but format it which I don't want to do, because there are many important files. Any suggestion to repair unmounted external hard drive or recover data?

external hard drive not mounting on Mac disk utility

When you connect an external hard drive to your Mac, it will show up on Mac Desktop, Finder and Disk Utility. But sometimes the external drive won't show up on any of these places. So, data inside the unmountable external hard drive turns inaccessible.

Don't worry, read and apply the below soluitons to resolve external hard drive not mounting issue.

Unable to mount external hard drive, how to fix it?

There are five solutions to fix external hard drive not mounted issue on your Mac:

1. Change macOS Settings

Ensure Finder preference to show external disks on Desktop or Finder is enabled.

Step 1: Open Finder from Dock. Click Finder and select Preferences.

Step 2: On the "Finder Preferences" window, click the General tab.

Step 3: Under "Show these items on the Desktop" section, check "External disks" option. The external hard drive will show up on your Mac desktop.

Show items on Mac desktop

Step 4: Click the Sidebar tab. Under "Locations" section, check "External disks" option. The external hard drive will show up in Finder sidebar.

Finder Preferences sidebar

Step 5: Open Applications, Utilities and Disk Utility. Click the View menu located at the top left corner of Disk Utility and select "Show All Devices". Your Disk Utility's sidebar will show the external hard drive.

2. Fix external hard drive connectivity issue

The first thing you can do is to ensure that your external hard drive is connected to your Mac properly. Here are some things you can try:

Reconnect the USB connector or adapter to fit the hard drive snugly
Connect the hard drive to a different USB port or a different Mac
Replace the USB cable or adapter in case that it was damaged or broken
Connect it to a Windows PC and see if the external hard drive is powered on and working

3. Repair unmounted external hard drive with Disk Utility

First Aid is a utility built-in Mac operating system. It can check and repair file system errors on Macintosh HD, external hard drive, USB flash drive, SD memory card, etc,.

Steps to fix external hard drive not mounting issue with First Aid:

Step 1: Open Applications folder, select Utitities and Disk Utility.

Step 2: In the left panel of Disk Utility, select the problematic external hard drive.

Step 3: Click "First Aid" button in the toolbar of Disk Utility.

First Aid built-in Disk Utility

Step 4: Click "Run" button, First Aid will check the volume for errors and then fix the problem if possible.

Wait until the procedure is complete. If you get returned a message saying success, restart your Mac and see if the external hard drive is mounted.

If another message says that disk utility cannot repair the disk, go to solution 4 to recover lost data.

Disk utilily cannot repair external hard drive

4. Recover data from unmountable external hard drive

M3 Mac Data Recovery is a professional Mac data recovery software. It can recover lost data from corrupted, unreadble, unmountable external hard drive.

M3 Mac Data Recovery is fully compatible with macOS Catalina 10.15/10.14/10.13/10.12 and Mac OS X 10.11/10.10/10.9/10.8 and supports APFS, encrypted APFS, HFS, HFS+, exFAT and FAT32 file systems.

Steps to recover data from unmountable external hard drive:

Step 1: Download, install and then launch M3 Mac Data Recovery on your Mac computer.

Step 2: Select the volume or external hard drive.

Free Mac data recovery software - M3 Mac Data Recovery

Step 3: M3 Mac Data Recovery is scanning lost data from unmounted external hard drive.

Scan lost data from unmounted external hard drive

Step 4: After the scan completes, you can check and preview the found files.

Recover lost data from unmounted external hard drive on Mac

M3 Mac Data Recovery can preview documents, photos and play videos, audios so that you can see if your lost files are recoverable.

Step 5: Select the needed files and click Recover to start recovery.

After data recovery is successfully done, you can reformat this external hard drive and make it working again.

5. Erase the external hard drive

If this external hard drive doesn't have important data, format is the best choice to make it usage.

Step 1: Open Applicatins folder, select Utilities and select Disk Utility.

Step 2: Select this external hard drive from Disk Utility sidebar.

Step 3: Click "Erase" button in the toolbar of Disk Utility.

Erase the drive

Step 4: Select file system and then click "Erase" button, the unmountable disk will be working again after erasing.

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