Installation of Exchange 2013 Failed on Mailbox Role Transport Service

Hi All,

Getting this error when trying to install a new exchange 2013 server. Thanks in advance

Error:
The following error was generated when "$error.Clear();
          if ( ($server -eq $null) -and ($RoleIsDatacenter -ne $true) )
          {
            Update-RmsSharedIdentity -ServerName $RoleNetBIOSName
          }
        " was run: "Microsoft.Exchange.Data.DataValidationException: Database is mandatory on UserMailbox.
   at Microsoft.Exchange.Data.Directory.ADDataSession.Save(ADObject instanceToSave, IEnumerable`1 properties, Boolean bypassValidation)
   at Microsoft.Exchange.Data.Directory.Recipient.ADRecipientObjectSession.Save(ADRecipient instanceToSave)
   at Microsoft.Exchange.Management.Deployment.UpdateRmsSharedIdentity.Link()
   at Microsoft.Exchange.Management.Deployment.UpdateRmsSharedIdentity.InternalProcessRecord()
   at Microsoft.Exchange.Configuration.Tasks.Task.<ProcessRecord>b__b()
   at Microsoft.Exchange.Configuration.Tasks.Task.InvokeRetryableFunc(String funcName, Action func, Boolean terminatePipelineIfFailed)".