I've got a Seagate FreeAgent GoFlex Desk 2TB External USB 3.0/2.0 Hard Drive that I use for backups.
I previously had issues with USB ports not supplying sufficient power to the drive, but that was resolved by plugging into back-plate ports on back of case, rather than case ports. Now it does not connect/mount when plugged into the same port(s) in the back of case, but the drive isn't bad cause it's fully functional on USB 2.0 ports.
Drivers haven't changed and don't show any issues, so I can't really explain this one. Disk Management doesn't pick it up either, and not as unallocated space as one might expect. In all my experience with computers, they don't just suddenly change their ways unless prompted to do so.
How can I troubleshoot this further?