When running a backup, you may encounter the error "Unknown VSS or COM error".
Message: 10:05:06 Starting VSS snapshot
Error: 10:05:07 An error occurred trying to initialize VSS: Unknown VSS or COM error
Warning: 10:05:07 VSS could not be started and was disabled
You may also find that the VSS writers are not shown in the ESE agent when trying to backup Exchange or MS SQL using VSS.
A common cause of this issue is having the 32-bit ESE agent installed on a 64-bit operating system. VSS will not function when running as 32-bit on a 64-bit machine. If you used the default path when you installed your agent, you may notice "(x86)" in the installation file or working paths (e.g. C:\Program Files (x86)\Attix5 Pro\Backup Client SE\toBackup), indicating that 32-bit program files are being used.
To resolve the issue, uninstall the 32-bit agent, install the 64-bit agent, and reconnect to the account. Be sure to also reinstall any applicable plugins.