Acronis True Image: unable to select a disk for new backup, already configured backups fail, if volsnap is missing from UpperFilters in the system registry

Symptom 1

Entire PC backup interrupts with message "Source is not selected. The operation has been terminated".

Symptom 2

After interruptions and retries, illustrated above, Entire PC backup transitions to the "failed state" and a red cross is displayed. The error text says "Source is not selected. The operation has been terminated".

Symptom 3

If you try creating a new "Disk and partitions" backup, "OK" button is grayed out and a message appears: "Unable to back up a locked volume encrypted with BitLocker. Unlock the volume or turn off BitLocker, and then try again.", even though the selected disk volume is in "unlocked" state (see Compatibility with Bitlocker).

Cause

Acronis True Image uses Microsoft Volume Shadow Copy service (VSS) to access disks for backup. If there is any problem with VSS, backup may not work properly.

The above described symptoms can occur when "volsnap" entry is missing from UpperFilters under the key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{71a27cdd-812a-11d0-bec7-08002be2092f} in the system registry.

volsnap is the Volume Shadow Copy driver and is required to not only be up and running, but also present in the aforementioned registry key, for Microsoft Volume Shadow Copy service to function correctly.

volsnap could have been erroneously removed from the registry key by a third-party software, e.g. antivirus or a system optimization software.

Solution

Add the missing volsnap entry in the system registry resolve the issue:

1. Make a backup of the folder, where the system registry is stored C:\Windows\System32\Config as a precaution measure, by using Acronis Bootable Media. Alternatively, you can create a backup of the whole system disk with the same bootable media.
2. Back in Windows, add volsnap in the system registry:
   1. Open Windows Start menu, type regedit, press Enter on keyboard
   2. Navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{71a27cdd-812a-11d0-bec7-08002be2092f}
   3. Double-click on UpperFilters in the registry editor.
   4. Add volsnap on a new line beforefltsrv, so that all entries in the box "Value data" are written one per line
      
   5. Click OK
3. Reboot the computer