The Mojave cannot recognize external hard drive.

Do you happen to have a Seagate external drive? Seagate is not supporting the latest update to High Sierra either. I found a couple options and I have emailed Seagate. Before I post further let me know if you are using Seagate. We both may be out of luck with new iOS being unsupported.

No, that is no what the issue is. The issue is Mojave and your answer is about Sierra. My drive worked fine with Sierra, and my drive is a WD, so as has been stated correctly by others, and even by you (Paragon) you need a 3rd party software to mount or access your external drives. This is utter nonsense for a company like Apple that touts being the most advanced etc. No reason for it other than their proprietary tit for tat BS. Of course I want my external drive to work for Windows and Mac both, as the whole world still uses both OS...

I posted my issue on a separate post the other day-but received little help. So since I have almost the same issue as the initial poster, thought I'd post here instead. I've owned Macbooks and iMacs and I have never had issues like I have had since upgrading my 2017 MBP to Mojave this past Dec. My problems began when I upgraded to Mojave (from the latest version of HS)- I keep things updated very well. I initially noticed that it would freeze and the only way to fix the issue was a power off. Then I noticed that my External HD (Mac OS Journaled Ext) that I have only had for a few years would take forever to load up and eventually show my files. Took up to 10 minutes sometimes. So I decided to do a fresh install of Mojave. Did a TM backup and a CCC backup. Reinstalled Mojave as a NEW Macbook Pro without loading my backup. Had some issues with FileVault, so I wiped and reloaded it again for the 2nd time. I worked on it a bit and it seemed fine so I slowly loaded some apps little by little before advancing too much further. Then I eventually plugged my external hd in. Same thing happened-except now it got to the point it would not even show up in Finder. Bought a new USB cord-not the issue. So I rushed out and purchased a new WD external HD with USB-C (formatted it APFS instead of Mac OS Journaled after reading it was best to use with Media/Images and with Mojave). It was awful trying to move files over when the other EHD wouldn't show up in finder but after a week, I eventually got them all moved over to the new external hard drive by plugging it into my NAS Drive on my network. So when I had no issues with this new EHD, I assumed it was my old external hard drive with an issue that just coincided with the Mojave update. Especially since a couple of my other older EHD worked fine with Mojave from the get go. Anyway, I have been using the new drive now for about 4-5 weeks and have had no issues until last week when all the sudden I notice that files are missing that were there! Sound familiar? So after a few hours, I plugged the new USB C HD in again-and NOW it won't show up either. Again, older EHD's will show, but this brand new one won't all the sudden just like my other EHD did. It shows in Disk Utility but doesn't show how much of the EHD has been used. I tried safe mode, reset SMC, PRAM - didn't fix it. So I now have 2 external hard drives (formatted differently) that have been bricked by Mojave. Took it to Apple and they eventually decided that nothing was on the external hard drive and I disagreed. They wanted to wipe it for me-I said no. They suggested that APFS formatting on be done on SATA Hard drives, not external hard drives because they do not play well with Mojave and APFS. WHAT? Anyway, my first External that quit showing up was formatted Mac OS Journal Extended. So I went back home and purchased Boysoft data recovery software and it has found all my files so far. So I am trying to recover the files that I had added in the last few weeks (all others were backed up thankfully). And it gets better - the first external hard drive that stopped showing up on Mojave back in December that started all of this, now shows up perfectly fine in Mojave. WHAT?

So my concern is that this has now happened to me twice on external hard drives - why? And yesterday, I had another external that stopped showing up in Finder, but would show on my desktop. Praying it isn't doing the same thing. Any suggestions or any info that has been discovered since this initial post?

This works also for IMac computer OS Mojave to recognize Seagate external hard drive plus https://m.youtube.com/watch?v=DVgMd4unhTQ

Try another USB cable is the easy first try.

I have one drive (single-cable USB 3) that simply WILL NOT mount on a friend's iMac but will on mine reliably. When I swapped cables for a thicker one, that's the only difference I saw, it mounted as expected on both Macs.

You could also try resetting the NVRAM and SMC and also boot into Safe Mode then reboot right after not in Safe Mode.

Safe Mode = Boot with Shift held down until you see "Safe Mode" on screen. This purges lots of cache files. Then reboot again normally.

Safe Mode

https://support.apple.com/en-us/HT201262

NVRAM reset

https://support.apple.com/en-us/HT204063

SMC reset

https://support.apple.com/en-us/HT201295

Sorta often the Mac needs to clear its caches and things after an OS update.

I have Samsung M3 USB3 that The Mojave cannot recognise anymore.

also tried resetting the NVRAM and SMC and also boot into Safe Mode then reboot right after not in Safe Mode, nothing happens. I can see it on USB tree and also in Disk Utility, but can't mount it... in Disk Utility it seems grey and can NOT be mounted.

Any idea?

Hello Zolablue - yes I have a Seagate. Background info: prior to upgrading my Mac to Mojave, my Seagate hard drive could function perfectly fine (on both Mac + PC) and read + edit files (mostly documents, pictures, nothing too big) I had saved from my Windows PC (I work with both laptops) onto my hard drive. Now, my Mac "sees" the Seagate hard drive but it is greyed out and I can not mount it/ not do anything really. I contacted Apple support and they said I had to reformat the whole hard drive. But even if I do so (after saving my docs on a different drive or computer), how will I ever be able to use my saved documents from the hard drive on my Mac? I am lost and need to work on these documents 😟 If anyone can offer advice? Many thanks!!

Thank you Old Toad. What is the software please? I downloaded iBoySoft but even that can't mount the drive. I am at a loss here as my drive now can only be read by a Windows PC - I am not sure how to get my documents back... Hopefully the software you are talking about is the solution! 🙂 As for the photo library - I don't use iPhoto - just jpg docs. Many thanks for your help!

This has been happening to my iMac since I upgraded to Mojave. Usually about 10 minutes after my machine boots up it kicks my hard drive off. Since the OS upgrade my external icon shows TimeMachine but my time machine is turned off and has been for 2 years. Previous to the upgrade the icon was always orange.

I've literally been working with Apple tech support for 2 months without any resolution. It sucks b/c all my iTunes resides on my external.

WD is doing the same thing. I have been using WD for the past few years never had any issues. The Update before this Movjave made another hard drive stop mounting. Now I updated again and My main hard drive wouldn't mount. I have recently been having the issue of it mounting and not being able to transfer files. Why is the update messing with External hard drives??

I also am using a Seagate external hard drive and it isn't compatible with my macbook anymore since i've updated to Mojave. So we're out of luck? We can only use the external hard drive again if we get a new computer?

That did not solve the issue. Again apple need to fix this problem. I want to use the music I have on my hard drive that I personally took the time to organize the way I wanted it. And now they updated again and the problem is not fixed.

Nothing on this post works. This is a Mojave apple issue.

One thing i've noticed (my "senior tech support" person said this isn't part of the problem-I don't believe her) is that pre-Mojave my external hard drive icon was orange b/c I have time machine shut off. I noticed the problem began when the icon turned back to a Time Machine icon, even though i've completely shut down time machine on my iMac and it doesn't point to any drive anywhere. There is an issue there somewhere and they clearly don't believe me even though i've down countless scsitracer and other data dumps to them.

Same problem. My old samsung hard drive would let take thing out of it but not modify it in anyway. I thought it was the HD dying out, so i bought a G-Technology one. Connected it, nothing could be moved in. Format it, it wouldnt mount if its any format except ExFAT. Ias ExFAT, tho it mounts, won't let me modify anything. Tried it on a PC, it works fine. Did all the SUDO things in the terminal, wont work. Talked to apple, they made me change the permissions and everything on the whole computer and old drive and new drive, nothing. The new drive in GET INFO wont even allow me to see options. The triangle just wont display anything but the phrae "read only" thou with the apple rep we bypassed any permissions from the finder and terminal. They told me reinstall mojave. Same same.

Need answers people. Solutions. What the f*** is wrong with mojave.

I have the same issue. I did the NVRAM and SMC but nothing changed. My usb tree shows the device (Seagate External) but I can't see it in Finder, Can't see it in disk Utility Either.

What can you do if you can see it but both NVRAM and SMC don't work