Event 375 - 0x80040155 - When Exporting using Enterprise Vault Discovery Accelerator

Problem

An Enterprise Vault (EV) Discovery Accelerator (DA) review or export encounters error message "An internal failure occurred. Internal Error: 'Interface not registered [0x80040155]'. " and Event ID  375 is logged in the event logs.
 

Error Message

System.InvalidCastException: Unable to cast COM object of type 'System.__ComObject' to interface type 'IStorageOnline2'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{DDAA2295-3AF2-441A-AAA4-983E6549409B}' failed due to the following error: Interface not registered (Exception from HRESULT: 0x80040155).

Message : The original item cannot be displayed.\r\n\r\nUser:\t\SYMC_AMERICA\evault1\r\nCustomer:\t2\r\nServer:\t\tlocalhost\r\nDomain:\t\tAccelerator Client Domain\r\nStack:\t\tApp.App_DispatcherUnhandledException\r\n\r\nInner exception:\r\n   at Accelerator.Client.Review.NativeDownloadManager.<>c__DisplayClassa.<ViewOriginalThread>b__3(Object arg)

Cannot retrieve item 
Report this error to your system administrator 
An internal failure occurred. Internal Error: 'Interface not registered [0x80040155]'. 
 

Event Id 375 is logged in the event logs

Event Type: Error
Event Source: Accelerator Service Processor
Event Category: None
Event ID: 375
Description:
APP AT - Customer ID: 2 - An Error has occured when retrieving Item
SaveSetID: 201008172051839~200711011315310000~Z~90029CC4A97FFC0873535B0AB55D7471
VaultID: 116BC6BA5C4E8AD46AAA708462D916CFF1110000EV7Site
Format: MSG:U
sAttachmentID: 0.
System.InvalidCastException: Unable to cast COM object of type 'System.__ComObject' to interface type 'IStorageOnline2'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{DDAA2295-3AF2-441A-AAA4-983E6549409B}' failed due to the following error: Interface not registered (Exception from HRESULT: ).
   at KVS.Accelerator.Common.EVStorageOnline.LoadStorageOnline(Boolean bForceReload)
   at KVS.Accelerator.Common.EVStorageOnline.GetOnlineAttachment(String savesetId, String vaultId, String attachmentNum, String format, Object& oByte
V-437-375

Cause

The cause of this error is the failure to properly register the StorageOnlineOpns.dll file on the DA server.

Solution

On the Discovery Accelerator server register StorageOnlineOpns.dll with Regsvr32.exe

From a command prompt, type (where Enterprise Vault is installed to default installation path)

regsvr32.exe "C:\Program Filesx86\Enterprise Vault\StorageOnlineOpns.dll"

If Enterprise Vault is not installed to the default installation path, change the drive letter and path to the where Enterprise Vault is installed.