Exchange 2013: RPC Proxy can't be pinged.

Hi,

Clients cannot connect via RPC over HTTPS.

Attempting to ping RPC proxy mail.domain.co.nz.
 	RPC Proxy can't be pinged.
	Additional Details
 	A Web exception occurred because an HTTP 404 - NotFound response was received from Unknown.

I can confirm /rpc/rpcproxy.dll is working.

All URLs are set correctly. I have noticed the following in  the event log

Event code: 3005 
Event message: An unhandled exception has occurred. 
Event time: 22/04/2013 10:15:33 a.m. 
Event time (UTC): 21/04/2013 10:15:33 p.m. 
Event ID: 6b9521dc6bf14602adeaefe8b6745571 
Event sequence: 1551 
Event occurrence: 1550 
Event detail code: 0 
Application information: 
    Application domain: /LM/W3SVC/1/ROOT/Rpc-23-130107909133275772 
    Trust level: Full 
    Application Virtual Path: /Rpc 
    Application Path: C:\Program Files\Microsoft\Exchange Server\V15\FrontEnd\HttpProxy\rpc\ 
    Machine name: CL-CAS01 
Process information: 
    Process ID: 640 
    Process name: w3wp.exe 
    Account name: NT AUTHORITY\SYSTEM 
Exception information: 
    Exception type: HttpException 
    Exception message: The client disconnected.
   at Microsoft.Exchange.HttpProxy.ProxyRequestHandler.EndProcessRequest(IAsyncResult result)
   at System.Web.HttpApplication.CallHandlerExecutionStep.OnAsyncHandlerCompletion(IAsyncResult ar)

 
 
Request information: 
    Request URL: http://cl-cas01.domain.local/rpc/rpcproxy.dll?05a33d51-8faf-43ba-a261-1cf82c0e8ae8@domain.co.nz:6001 
    Request path: /rpc/rpcproxy.dll 
    User host address: 10.100.10.31 
    User: domain\test_user
    Is authenticated: True 
    Authentication Type: NTLM 
    Thread account name: NT AUTHORITY\SYSTEM 
 
Thread information: 
    Thread ID: 24 
    Thread account name: NT AUTHORITY\SYSTEM 
    Is impersonating: False 
    Stack trace:    at Microsoft.Exchange.HttpProxy.ProxyRequestHandler.EndProcessRequest(IAsyncResult result)
   at System.Web.HttpApplication.CallHandlerExecutionStep.OnAsyncHandlerCompletion(IAsyncResult ar)
 
 
Custom event details: