The external storage device could not be recognized.
Unplug and plug the storage device.
Make sure your storage device could be working well on other system.
Check any physical damage on port or slot.
Swap a storage device.
Logging: (If you can’t resolve the issue, please submit the following information to Yeastar)
Post us the test result of the check list.
Post us the System Log (S-Series), Dmesg Log (U-Series & Gateway)