Not recognizing external hard drive

I had the same issue. My Finder was not recognizing my seagate external hard drive when connecting it to may Macbook Pro. Interestingly I left the driver in and after 6-7 it recognized it. This has since happened several times. I cannot explain why.

The only thing I've seen make USB drives vanish is NTFS drivers added to OS X, of any brand. If I need to have a drive be accessible by both OS X and Windows I just format it as ExFAT.

I have a MacBook Pro and have been using an Rugged All-Terraiin HD to store my photos. This system has been working fine for over a year, then one day it just wasn't recognized. I tried several of the suggestions on line before downloading any thing. Then read the manual for the HD and it mentioned 'if the usb bus on your computer doe not provided the necessary power to operate the HD, connect the USB power cable...' Hmm? I had never had to use this cord before, but I tried it and it worked. Whew!!! 40K photos

I have a 4TB Passbook and in accordance to what everyone else is saying this thing is sensitive to power supple. I guess with all your precious information inside it should be. However my solution was quite different, and sort-of unexpected. To help anyone else who may be having this problem read on:

I had the correct power supply. There was almost 0% chance that I had accidentally swapped it with another. However I did plug it in to a Energy Surge protector. This was causing the problem of the drive not mounting/not being recognized by my iMac. So I unplugged it from the surge protector and plugged it in to a normal extension strip and voilà there it was, sitting pretty on my desktop.

This kinda worries me though, that I can't plug it in to a surge protector. I live in Brazil, and it is currently rainy season, so lot's of lightning. I lost a few things (including most of the internal parts of this iMac) to surges. I wonder if there is a way around this.

I had an identical issue with my Seagate external 1TB drive, which I've been using consistently for a few years (set up this machine with it from a previous Time Machine backup and have had no problems with it on either the old or new machine). This past backup failed - I tried to back up and could not see the drive. Tried all the regular things (plugged it, unplugged it, checked the cable, multiple USB ports, rebooted, etc etc).

When I saw this thread, I went into System Information and then Time Machine from there (just using the Time Machine prompt said it couldn't see the drive). However, in settings, the machine saw the drive -- but appeared to recognize it as a separate entity from the one assigned to Time Machine...I reselected it, and it worked. However, at no point did it show in finder or appear to be mounted. The backup is running as of this moment.

After months of not using my WD hard drive I decided to plug it into my MBP to backup the system but it wouldn't appear on Finder like it usually does.
So I searched for "Disk Utility" > select the WB hard drive and clicked "Repair disk". Once the repair is complete, it was back on Finder.

Hope this helps anyone at all. 😉

Formatting my drive worked for me: Format external drives to Mac OS Extended before using with Aperture - Apple Support

This is the step if your drive didn't recognised by System Profile.

You need another Mac to read your drive. On that another Mac, you need to view the hidden files.

Steps to view hidden files:

1. Open Terminal found in Finder > Applications > Utilities
2. In Terminal, paste the following: defaults write com.apple.finder AppleShowAllFiles YES
3. Press return
4. Hold ‘alt’ on your keyboard, then right click on the Finder icon in the dock and click Relaunch.

Select each partition on external drive and delete all hidden files except .Trashes

This time, make sure you Eject your external drive properly.

Plug in the drive to your Mac.

Same problem. Following sequence seems to fix it:

• Unplug the Passport drive
• Power down
• Startup in "safe" mode (hold down the shift key as soon as you hear the chime and continue to hold until the turning gear appears)
• Restart
• Plug in Passport external drive

Now the Passport is recognized in Finder and the backup was able to proceed.

Called AppleCare, but these posts gave me a solution before Apple came off hold from researching the error.

Thanks! Your post helped me resolve my problem with the external drive!

Same problem with with an iMac. Following sequence seems to fix it:

• Unplug the Passport drive
• Power down
• Startup in "safe" mode (hold down the shift key as soon as you hear the chime and continue to hold until the turning gear appears)
• Restart
• Plug in Passport external drive

Now the Passport is recognized in Finder and the backup was able to proceed.

Called AppleCare, but these posts gave me a solution before Apple came off hold from researching the error.

Hey All,

So I just had this problem. My Macbook Pro Retina 13' Mid 2014 all of a suddenly didn't recognize my two (8gig) (32gig) Sandisk USB drives and my 1tb WD my passport external hard drive. I follow the advice of starting my computer in safe mode and then it recognized my two USB drives. But it still didn't recognize my WD external hard drive. So repaired it and all, but realized that it was the usb cord. My external HD gets it power from my macbook pro through the usb cord. I used the cord which to charge my samsung phone and it worked just fine.

just ran into this issue. I also have a WD HD that I share between PC and MAC.

Solution: The HD was not properly ejected from the pc. Plug the HD back to a PC and ejected properly. Then plug it back into a MAC and it should be recognized.

good luck.

I had the same problem and found to that I needed to download a third party driver:

http://www.seagate.com/support/downloads/item/ntfs-driver-for-mac-os-master-dl/

Paragon Driver for Mac OS | Seagate

Seagate Technology

I had the same issue. But after the latest OS update(El Capitan) external HDs and pen drives are working fine.

Thank you Ella - that just saved me a bunch of time! Thought that was the end of my TB, but you saved the day! 🙂