External drive no longer recognized.

Not sure if the firmware update directly affected the hard drive in question; if

you have access to another computer, you could see if the drive itself is OK.

Another possibility is that hard drive chose the time to fail (the enclosure, perhaps)

that coincided with the update; the drive inside the housing may be fine. And at

times, a hard drive could be located by using Disk Utility while not visible on the

desktop. Sometimes if an external drive gets interrupted during a read-write, it

may fail to appear later to the computer. At times, a different cable may help. Or

if available to test with another adapter, too.

Did you read this other thread of similar issue for ideas?

USB-C Multiport Adapter update not installing

Sometimes an external drive or other attached device may be seen again after

a re-start; or after an SMC re-set. Not a sure thing, though.

Sorry to not have a specific workable reply to cure this ailment.

Good luck in any event...! 🙂

I have the same problem frequently with external drives. The drive powers up, but the OS does not see it. Even the disk utility is unaware that it is there. The only fix I have found is to reboot the MacBook, and try again. Usually, it works. And here I thought I had left the "reboot to fix problems" thing behind when I moved to MAC. Oh well.

I had the same problem with 10.11.4 and it was not an issue of the multiport adapter bacasue usb flash drives connected directly to the USB-C port have shown the same problem . I restored 10.11.3. just to see if this is an OSX problem an d with 10.11.3 the problem is gone. The USB drives are always recognized properly.

I already reported this to Apple via the feedback report sheet and my hope is that Apple will fix this asap. Until this happens i will keep 10.11.3 installed on my MacBook .