in-place eDiscovery & hold 'The request failed. The underlying connection was closed: An unexpected error occurred on a send.'

Hi,

Hoping for some help with an Exchange Server problem I am having.

Everything else on the Server seems fine.

Build Number: 15.0.995.29 (CU6)

However when I use the ECP to try to do a Compliance Management / in-place eDiscovery & hold

This appears in the right hand column;

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Status:                                                Search Failed                    

Also in powershell;

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[PS] C:\Windows\system32>new-mailboxsearch -name "test" -TargetMailbox "kev" -SearchQuery "'jean-pascal'"
Creating a new session for implicit remoting of "New-MailboxSearch" command...
The request failed. The underlying connection was closed: An unexpected error occurred on a send.
    + CategoryInfo          : NotSpecified: (:) [], DataSourceOperationException
    + FullyQualifiedErrorId : [Server=CCMAIL03,RequestId=fa226efb-fe18-4a12-8ea2-d36e23711d87,TimeStamp=19/11/2015 13:
   13:27] [FailureCategory=Cmdlet-DataSourceOperationException] 8029597E
    + PSComputerName        : ccmail03.carmel.local

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Have checked as many obvious things as I can, sure it will be something blindingly obvious!

TIA!