EMC DD – Error: Failed to call RPC function ‘DDBoostFcWriteFile’: Failed to open file ‘

To resolved this issue in version 12 follow this procedure:

1) Download the fix https://storage.veeam.com/Fix_550082_e27e09c2c3.zip  and unzip it to a temporary location.
2) When possible, stop the Veeam Installer service
3) Then go to this location: C:\Windows\Veeam\Backup
4) Rename the VeeamDeploymentDll.dll to VeeamDeploymentDll.dll.orig
5) Copy the DLL from this fix you unzipped to the same location (C:\Windows\Veeam\Backup)
6) Repeat steps 4 and 5 for the additional locations below as needed (some paths may not exist on all managed servers, replace in all that do):

C:\Program Files (x86)\Veeam\Backup Transport\GuestInteraction\VSS\Packages

C:\Program Files\Common Files\Veeam\Backup and Replication\Mount Service\Packages

C:\Program Files\Veeam\Backup and Replication\Backup Catalog

C:\Program Files\Veeam\Backup and Replication\Backup\Packages

C:\Program Files\Veeam\Backup and Replication\Enterprise Manager

C:\Program Files\Veeam\Veeam Distribution Service\Packages

7) Start the Veeam Installer Service
8) Retry the backups