Why not upgrade OSX.

Did you use the scrict procedure ? There’s a known problem with mac witch is USB ground and OT. So there’s a plug order (like rewire order if i can describe like that)

  1. Power the MAC (wait for it’s ready)
  2. Plug the OT usb (but OT is power off)
  3. Switch on the OT
  4. Go in system activate USB Disk mode (at this point OT mount if not upgrade your OSX)
  5. Eject everytime the OT by drag and drop on the trash to eject.

Then workaround is cheap card player