My Transcend external hard drives can't mount after OS Sierra upgrade.

Hi again, I started a thread a few days ago, but all I got was to reset the NVRAM and unplug the cpu, which I did.

Not sure if these are ntfs or hfs, this is a desktop screenshot. I am waiting for a new drive to arrive to back up Sierra. Do you know which format I should be using?

Dot.com, I've got a Mercury. I did download Paragon ntfs as a trial and they showed up, but why do I need to download software when I never had to do so before? Apple always showed external hard drives without having to purchase or download extra software. :/

NTFS is only officially supported for read-only from OS X - it kind of supports writes but not reliably from what I've read - hence the Paragon and others support software. If you only want to look but not write on volume then you're OK.

Where do you see that Apple supports NTFS write mode in a reliable fashion.? It's been like this for as long as I'm aware.

I'm not a computer whiz, so bear with me. I have 4 Mercury HD's that I've been using, 2 bought in 2010 and 2 bought in 2014. I've used SuperDuper to make bootable backup drives and they've always mounted and I have never had a problem until Sierra. So what do u think is happening? What has changed?

Well, don't know anything about SuperDuper! Checked their web site and they say that Sierra is supported but it says it only copies HFS+ volumes - nothing about NTFS volumes. Are your Mercury HD's HFS+ or NTFS or ???

If you do a "Get Info" on the volume (Commnd+i is the shortcut), you will see the format of the volume listed as one of the parameters like when created, capacity, etc.

I'm not familiar with Mercury or Transcend really other than Mercury is OWC brand of external drives and Transcend is another external drive manufacturer of high performance drives. Are they related in some other way? If not, you might consider to really start another post rather than proceed with discussion here, if it's nothing to do with original Transcend NTFS question.

Good luck...

Please go back to your original post and repost these images and I will reply there...

These parallel discussions (multiple discussions going on in the same thread topic) can be very confusing to everyone.

Even with the latest upgrade to 10.12.5 !! This is truly embarrassing for Apple, and ME!!. I can't get important photos off an external. USB is useless. Thanks Crapple. <<dedicated user since 1991 too!!

I couldn't find it, either. I think it was in another thread that was already started. Here's the new post link:

Mercury Hard Drives won't mount in Sierra

An SMC Reset has been known to fix that. Try it: Reset the System Management Controller (SMC) on your Mac - Apple Support.

You may want to check Transcend support…

https://ca.transcend-info.com/supports/service.aspx

Do I have to keep doing SMC resets until the problem gets solved?

No. One should have been enough.

Does the external drive appear in Disk Utility?

Did you apply the macOS 10.12.2 update? Check the App Store > Updates or Download macOS Sierra 10.12.2 Combo Update.

My Mercury won't mount, either.

What is the filesystem type on the Transcend volumes? Is it NTFS? If so, what software are you using for NTFS support? Have you checked for updates to that software for Sierra?

Good luck...

I can't find the post you seem to be talking about - so please put a link to it in a reply here so I know where to go.