Need Help w/USB Issue

[Hack5190]

Good day!

Have a USB issue with a 2015 MacBook Pro running Sierra where Disk Utility won't see a WD 5-TB USB-3 drive connected to a hub. Note that this configuration has worked flawlessly for over a year. The problem only surfaced recently in the middle of changing the partition layout and reformatting the WD USB drive.

The same hub & drive connected to a different MacBook Pro, 2016 running Sierra, works just fine.

Removing the hub or moving the drive to a different USB port on the 2015 and everything is good.

Adding another USB hub (downstream of the first hub) and connecting the drive to hub #2 - the 2015 sees the drive.

Based on the above tests it doesn't appear to be a hardware issue, but I am unsure where to look next.

Is there a USB explorer program that will force macOS to check / test / reset / rescan the bus and identify connected devices?

Does macOS block or lock out USB devices for some reason?

 

[Fishrrman]

Check the "conversations" area on your profile page...

 

[Hack5190]

Check the "conversations" area on your profile page...

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[Fishrrman]

USB chains can get flaky when a hub is introduced into the scheme of things.
Not all the time, but sometimes... often at the wrong moment.

If you "take the hub out of the equation" and are able to get done what you need to get done, well... just do it that way.

If after doing so, and then "putting things back the way they were before" results in a working configuration, well, smile at the thought "you got through it"...

 

[Hack5190]

The USB HD is used by Carbon Copy Cloner for nightly backups. Moving it to a different USB Hub (vs a different port on the same hub) seems to be the fix / work-around. Thanks for your help @Fishrrman.