External drive seen in Disk Utility but won't mount

It would appear the disk's filesystem is damaged and cannot be repaired. Usually, the only solution is to reformat the disk. Because this is an HDD, I assume it's formatted HFS+ which means you could try the tool Disk Warrior if you are willing to pay the tariff. DW may be able to repair the filesystem without losing any files.

Nothing stands out in the DriveDX report so I don't see any signs of the common types of failures. If you are hearing unusual noises from the drive, then it may have a mechanical issue. The "Seek error rate" in the DriveDX report looks a bit off, but unfortunately the drive manufacturer's don't explain or even standardize the reporting of this particular attribute so it really isn't useful in troubleshooting unless it triggers a failure notice. Combined with the noise and issues mounting the drive this attribute may indeed be indicating a near failure.

Now that you have recovered your data I would suggest erasing the physical drive and testing it thoroughly. Depending on how the drive sounds and behaves during testing will influence your decision on what to do with it long term.

nathanschwam Said:

"External drive seen in Disk Utility but won't mount:[...]Is there a way I can repair the external drive to access the files?[...]"

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A Few Thoughts:

• Try a New User:

Create a new Administrator user. See if you can then access the hard drive. If it works, then there is something misconfigured in your current user. So, just transfer everything over to the new Administrator user. Once transferred, trash this user.

• Remove Security Software:

If you have security software installed, uninstall it. Its firewall settings may be what is getting in the way here. A pure example of why Security Software just gets in the way on a Mac. Be certain to use the uninstaller for it --- download the uninstaller from none other than the Developer.

• Data Recovery Protection:

Being a damaged volume, data recovery can be quite pricey. So, next time you purchase a hard drive, you may want to get a protection plan or sorts for it. You'd likely find a protection plan pamphlet at the cash register of a retailer. It would be logical to purchase such a plan, as it would be much pricey less for data recovery, than would be going directly through a Third-Party.

Be careful in case the drive is physically failing. All attempts to repair the file system or attempts to recover the data could make a drive failure even worse. I would recommend checking the health of the drive by running DriveDX and posting the report here using the "Additional Text" icon which looks like a piece of paper. You will need to install a special USB driver in order for DriveDX to communicate properly with the external drive. However, not all external drives allow the necessary communication even when using the special USB driver.

If the drive is healthy, then Disk Warrior is a good choice to try and repair the volume.

If the data is really important, then you should consider contacting a professional data recovery service such as Drive Savers or Ontrack. Both vendors provide free estimates and both are recommended by Apple. You may only get one chance to recover the data so choose wisely on how you proceed.

In the future make sure to back up your system drive and any external drives you may have. Everything will fail at some point or you could accidentally delete something. This advice is even more important when using SSDs.