External hard drive not mounting Mac

After hours and hours of research and testing I solved this for me.

When I plugged in my external hard drive it showed up in my drive in Disk Utility but it was grayed out.

I could not mount my hard drives and it would not let me repair, erase, nor partition them, an old and a new one.

I decided to click on the view button at the top right corner of my disk utility app and I had "Show Only Volumes" selected. So I clicked on "Show All Devices" and this showed me each device the volumes were on. I could now select my external hard drive and I was able to easily repair, erase, and partition my hard drives when I clicked on the device instead of just the volume.

I hope this helps anyone.

YES, this is the fix. You need to go to the Disk Utility, click on the little View button above the drive window on the left (for some mysterious reason unknown to mankind). Then, under the external drives you'll see your peripheral, not grayed out. You can then erase or mount the peripheral. Additionally, I contacted Seagate and they have a new driver for mine available -- I also downloaded and installed that. However, it made no difference until I used the magic view button on the native Mac Disc Utility. (Two days, phone calls, emails, restarts ...)

APFS on your boot drive has nothing to do with it, your old HFS+ drives should work. That said, the most common reason for disks not mounting is that they are damaged. You can try repairing the disks using Disk Utility or DiskWarrior.

Click on View on Top Left of Disk Utility window and then select "Show all Devices".

Then select your external drive and click on mount. Wait for a minute or two, and it should show up again.

Thank you soooooo much for posting this. I had a similar problem - external disk (mac os extended) wouldn't mount on a brand new MacBook Pro with OS13.2, but I could see it greyed out in disk utility, and I was at a loss as what to do. But as soon as I clicked "Show all Devices", the drive suddenly appeared in finder, no problems at all. I did not have this problem with another drive - but that one was mac os extended journaled, not sure why that would make a difference in terms of it mounting, but oh well . . .

I had this problem too (and was freaking out!) I could see the ext hard drive was there, but it said the destination was not found and I could not access any of the files.

I opened a new window to see the devices menu, and right clicked on the Ext HD, then "get info".

In the bottom right corner there was a padlock symbol, which I had to press. Then it just asks for your password.

This seems to have fixed the problem.

It's deceptively simple, so I thought I would post in case anyone else had the same problem.

Restart seems to have solved my problem. 😕

Hello,

I had the same problem after High Sierra upgrade: impossible to mount the external hard drive (brand new Touro 2TB). After reading these posts, I tried to reboot the laptop without success. Using the laptop of my girlfriend (still on Sierra) I was able to mount and format (Mac OS Extended) the hard drive. Done that, I was able to mount it on my own laptop; I re-formatted it, just to see if there were some other problems before using it for time machine backup.

Hope this post can help you guys,

A+

I had a similar issue with the WD 1 TB after upgrading to High Sierra. I went to WD website: My Passport for Mac | WD Support and downloaded their utility tool. I ran the tool, erased the hard drive and got it working again.

Go to utility disk. Tap with to fingers the name of your external drive then click Run First Aid... then you’re good to use it.

Have you made sure that the drives are partitioned correctly - 'GUID' partition map? I have seen drives partitioned as 'MBR' format correctly as HFS+, then act squirrelly.

Have you tried restarting the computer while the drive is still connected?

I have the same problem with 3 of my 4 external drives.

I can access them in Terminal (/Volumes/), but they are not appearing in Finder.

If I use the common "open <drive's name>" I can access the contents, but the drives' names get mixed up.

Also Lightroom finds the drives, but also mixes up their names

I've just had this same issue.

I updated to High Sierra a couple of days ago and a 500GB external drive that was fine a few days ago suddenly wouldn't mount today.

I tried it in a Win10 machine while I was searching and found this forum post (it's FAT formatted) and the drive was fine, so after reading the replies here, I restarted my MacBook Pro and tried again and it came up immediately.

I have no idea why it happened or how it is now "fixed".

The only thing that worked for me was to leave the SD Card inserted and then restart my Mac, it mounted as usual after it restarted and I was able to download all the photos from my camera to my Mac. (The key here is to leave the disk plugged while restarting, I restarted unplugging the disk first and that didn't work.)

Thank you to whoever suggested this solution, the more complex ones didn't work, and I didn't want to first aid it because I know it wasn't a damaged disk.

This happened after I updated to MacOS HighSierra version 10.13.2 (17C88)

I hope this helps.