Error: VSS open files backup failed. Error: The provider returned an unexpected error code. in BCVssOpenFilesProcess Client Version = 11.2.61 (& higher)
This is often due to an old software package, i.e., backup exec, storagecraft, acronis etc. that was uninstalled from the system, yet left their VSS provider info in the registry.
Identify the errant VSS provider:┬áVSSadmin list providers at an admin command prompt. All you will see on a normal system is Microsoft Shadow Copy Provider. If you observe any other providers, then this is likely creating the conflict - especially if the referenced software package has been deleted from the system.
Fix this using regedit and navigating to following key: HKEY LOCAL MACHINE\SYSTEM\CURRENT CONTROL SET\SERVICES\VSS\PROVIDERS Then, look for the non-Microsoft shadow provider and delete that key. This is a common error on systems that have previously had Storagecraft ShadowProtect or Acronis previously installed (or a trial version) and then the software was subsequently uninstalled...leaving the residual registry key intact.
For more information, contact Technical Support.