Enable Password Writeback - Enable-OnlinePasswordWriteBack The given key was not present in the dictionary..

I'm currently trying to enable Password Writeback for Azure AD Premium. I've worked through http://msdn.microsoft.com/en-us/library/azure/dn688249.aspx and it appears that everything is set up correctly.

I've got to the point of enabling writeback in Powershell. The instructions don't seem to be valid for later versions of Dirsync as DirSyncConfigShell.psc1 no longer appears to exist so I'm running an administrative powershell then import-module dirsync then enable-onlinepasswordwriteback and receive the error Enable-OnlinePasswordWriteBack The given key was not present in the dictionary..

The below event is logged

Log Name:      Application
Source:        Directory Synchronization
Date:          07/10/2014 09:50:25
Event ID:      0
Task Category: None
Level:         Error
Keywords:      Classic
User:          N/A
Computer:      dc-dirsync.derby-college.ac.uk
Description:
System.Management.Automation.CmdletInvocationException: Unable to configure the password reset service: The given key was not present in the dictionary.. ---> System.ApplicationException: Unable to configure the password reset service: The given key was not present in the dictionary..
   at System.Management.Automation.MshCommandRuntime.ThrowTerminatingError(ErrorRecord errorRecord)
   --- End of inner exception stack trace ---
   at System.Management.Automation.Runspaces.PipelineBase.Invoke(IEnumerable input)
   at Microsoft.Online.DirSync.PowerShellAdapter.PowerShellCommand.ExecuteCommand(Command command, Boolean refreshPath)
Event Xml:<event xmlns="http://schemas.microsoft.com/win/2004/08/events/event"><system><provider name="Directory Synchronization"><eventid qualifiers="0">0</eventid><level>2</level><task>0</task><keywords>0x80000000000000</keywords><timecreated systemtime="2014-10-07T08:50:25.000000000Z"><eventrecordid>474418</eventrecordid><channel>Application</channel><computer>dc-dirsync.derby-college.ac.uk</computer><security></security></timecreated></provider></system><eventdata><data>System.Management.Automation.CmdletInvocationException: Unable to configure the password reset service: The given key was not present in the dictionary.. ---> System.ApplicationException: Unable to configure the password reset service: The given key was not present in the dictionary..
   at System.Management.Automation.MshCommandRuntime.ThrowTerminatingError(ErrorRecord errorRecord)
   --- End of inner exception stack trace ---
   at System.Management.Automation.Runspaces.PipelineBase.Invoke(IEnumerable input)
   at Microsoft.Online.DirSync.PowerShellAdapter.PowerShellCommand.ExecuteCommand(Command command, Boolean refreshPath)</data></eventdata></event>

I've worked with Office 365 support but they can't resolve the error. Anyone got any ideas?