Mac OS doesn't recognize external hard drive until I unplug and plug it back in

[leeskeys]

I'm running OS 15 Sequoia on a Mac Mini 4 Pro. I have a WD Black NVMe SSD external drive connected to one of the Thunderbolt inputs. I've noticed that when I start the computer, the OS does not recognize the external drive until I unplug it and plug it back in. After that all is well; I'm able to run the apps and open folders which are located on the SSD. Any idea why I have to unplug, then plug back in the external drive for it to be recognized?

 

[IWT]

Firstly: A warm welcome to Mac-Forums. And thank you for your post.

To get you started, here are some links which may help - or not, of course. Please post back to tell us if these helped.

External HDD's only connect after reboot. - Apple Community

discussions.apple.com

https://apple.stackexchange.com/questions/348303/macbook-pro-can-only-startup-with-external-hard-drive-connected

External Hard Drive Not Showing Up on Mac

MacKeeper ⭐ External hard drive not showing up on your Mac? ✅ Learn why your MacBook doesn't recognize your external hard drive and how to fix it

mackeeper.com

Ian

 

[pm-r]

I've noticed that when I start the computer, the OS does not recognize the external drive until I unplug it and plug it back in

Here are some other suggestions you might want to check out provided from a Google search for your problem:

Google Search

As one of the first suggestions they mentioned, have you tried using a different port and/or different cable to connect the external WD SSD?

Did the problem just start, and is it formatted for Mack use?

Do you have any other externals connected?




- Patrick
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[leeskeys]

The external SSD IS formatted APFS. The SSD enclosure is Cable Matters brand. It's plugged into one of the 3 Thunderbolt 4 sockets. I tried changing sockets, didn't make any difference. I've been away from my computer for a couple of days. It's been off. When I turned it on, it booted up but did not recognize the WD Black. I restarted and it didn't recognize it. I shut the computer down, then started it from scratch. It recognized the WD Black. And continued to recognize it the next 3 times I restarted. So, inconsistent is how I describe this issue.

Any further thoughts?

 

[RadDave]

The external SSD IS formatted APFS. The SSD enclosure is Cable Matters brand. It's plugged into one of the 3 Thunderbolt 4 sockets. I tried changing sockets, didn't make any difference. I've been away from my computer for a couple of days. It's been off. When I turned it on, it booted up but did not recognize the WD Black. I restarted and it didn't recognize it. I shut the computer down, then started it from scratch. It recognized the WD Black. And continued to recognize it the next 3 times I restarted. So, inconsistent is how I describe this issue.

Any further thoughts?

Hi Leeskeys - you've not mentioned what cables you are using, i.e. length and TB/USB specs? I recently tried to reformat a half dozen external SSDs (Samsung/ScanDiscs/etc) used on my older replaced computers - they were not recognized on my M2 MacAir laptop using a longest cable - then switched to a shorter TB3 cable and no problem - I'm assuming the length of the cable and possibly a lower TB standard did not provide enough power to the external drives - SO my suggestion is to try a shorter and better TB cable - may not work but did for me. Dave

 

[pm-r]

So, inconsistent is how I describe this issue.

For what it's worth, I have found inconsistency to be a feature of Mac OS 15 Sequoia I ended up using with my replacement Mark I purchased and so did using in January 2025.

I have never ever experienced such behaviors in the 35 years of Mac and much too often at least a restart as required and sometimes have to do several everyday. It drives me crazy and there is no reason for it to occur that I can find.

But the times it works properly and as expected is a very pleasant experience.



- Patrick
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[leeskeys]

the cable i'm using is integrated into the SSD case. I think it's maybe 8 inches.