Please follow the steps below::

1.) Close the Rbackup Endpoint completely. Stop rbackup.exe and rbclient.exe via task manager (If running).

Open the Registry Editor (regedit.exe) and browse to the following registry branch: 

For 32 Bit:

HKEY_LOCAL_MACHINE\SOFTWARE\Quantum Tech, Inc.\Remote Backup\Plugins\Exchange Server(VSS):

For 64 Bit:

 HKEY_LOCAL_MACHINE\SOFTWARE\wow6432\Quantum Tech, Inc.\Remote Backup\Plugins\Exchange Server(VSS):

KeyName: EseutilPath

KeyValue: (path of the Eseutil program, usually this location is the Exchange 'Install Dir'\Bin folder)

Make sure the value of the key "EseutilPath" points to the location of Eseutil.exe.

First run the DOS Command: vssadmin list writers

Run the DOS command: net stop vss

This should stop the volume shadow copy service. Make sure the status shows as manual.

Check for errors.

Restart RBackup Endpoint and start a backup with Backup Now.