HTTP 401 received when running exRCA and authentication fails

Question

After upgrading Exchange 2013 to CU6 our ActiveSync functionality stopped (along with a few other things). I have been using ExRCA to troubleshoot and have spent several days looking at forums and trying different things out to get it working again but to
no avail. Essentially when I enter valid account credentials it fails to authenticate and as a result I receive an 401 response.
I have already checked Inherited permissions are enabled for the user account in AD. I have checked that the authentication for the Virtual directory is set to Basic with SSL required. (Have also tried with windows authentication enabled). I have recycled
the ApplicationPool especially the MSExchangeSyncAppPool - That appears to be correctly configured and running under LocalSystem Identity. I have recreated the virtual directory using the reset feature in the EPC. Both internal and external URLs are set as
well as the CAS server being assigned to the External URL.
The report that I get: -         
An ActiveSync session is being attempted with the server.
 Errors were encountered while testing the Exchange ActiveSync session.
 Additional Details
Elapsed Time: 3721 ms.
 Test Steps
 Attempting to send the OPTIONS command to the server.
 Testing of the OPTIONS command failed. For more information, see Additional Details.
  Tell me more about this issue and how to resolve it
 Additional Details
An HTTP 401 Unauthorized response was received from the server. This may be the result of invalid credentials or a configuration problem on the Exchange Server.
HTTP Response Headers:
request-id: 216790d5-03dc-4616-87c6-d196c870a6f0
X-CalculatedBETarget: ex2013.domain.org
X-FEServer: EX2013
Content-Length: 0
Cache-Control: private
Date: Wed, 12 Nov 2014 16:13:10 GMT
Server: Microsoft-IIS/8.5
WWW-Authenticate: Basic realm="domain.org"
X-AspNet-Version: 4.0.30319
X-Powered-By: ASP.NET
Elapsed Time: 3721 ms.
I have failed request logging enabled and I am seeing numerous entries for some of the other services including ActiveSync and getting similar errors to the below: -
ModuleName
WindowsAuthenticationModule
Notification
AUTHENTICATE_REQUEST
HttpStatus
401
HttpReason
Unauthorized
HttpSubStatus
1
ErrorCode
No credentials are available in the security package
 (0x8009030e)
Any thoughts or additional diagnostic steps will be appreciated.
I tried recreating the backend virtual directory via EMC using the following command: - 
New-WebApplication  -Site "Exchange Back End" -Name Microsoft-Server-ActiveSync -PhysicalPath "C:\Program Files\Microsoft\Exchange Server\V15\ClientAccess\sync" -ApplicationPool MSExchangeSyncAppPool -Force
(didnt work...)

Answer 1

Hi Joby 
Thanks for getting back - tried your suggestion but still the same. 
Attempting to send the OPTIONS command to the server.
Additional Details
An HTTP 401 Unauthorized response was received from the server. This may be the result of invalid credentials or a configuration problem on the Exchange Server.
HTTP Response Headers:
request-id: 53f6bea6-4ef2-463e-87a1-f2dfd6a7bcf8
X-CalculatedBETarget: ex2013.xx.domain.org
X-FEServer: EX2013
Content-Length: 0
Cache-Control: private
Date: Mon, 24 Nov 2014 13:16:15 GMT
Server: Microsoft-IIS/8.5
WWW-Authenticate: Basic realm="xx.domain.org"
X-AspNet-Version: 4.0.30319
X-Powered-By: ASP.NET
Elapsed Time: 681 ms.