67078: Acronis Cyber Protect Cloud, Acronis Cyber Backup: Backup fails with "Operating system error: A device attached to the system is not functioning" and Event Code 8193

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Operating Systems: 

Last update: 29-04-2021


Backup fails with:

Operating system error: A device attached to the system is not functioning

In Windows Application logs, you see this error:

Source: VSS
Event ID: 8193
Level: Error
Volume Shadow Copy Service error: Unexpected error calling routine ConvertStringSidToSid(S-1-5-21-4148555394-1870526016-119506688-1000.OLD). hr = 0x80070539, The security ID structure is invalid.

The error can mention a SID either with .OLD or with .bak.


Invalid entry inside the HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindows NTCurrentVersionProfileList registry subtree.


  1. Open Windows registry (in Search, type regedit and press Enter).
  2. Navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProfileList
  3. Find the subkey specified in the error message (containing .bak or .OLD). Back up the subkey: right-click and select Export.
  4. Delete the faulty subkey.
  5. Reboot the machine.