Users get below error when try to login to CWA (Communicator Web Access) on Office Communication Server 2007 / R2.
“A problem occurred and the session was ended. Please sign in again. If the problem persists, contact your system administrator.(Error code: 0-0-18401-0-0)”
There are Two possible causes for the above error code (1) Incorrect Certificate assigned on CWA, (2) There is a listening port conflict on the CWA Virtual server itself.
Refer below article to make sure the assigned CWA certificates are correct
Preparing Certificates for Communicator Web Access
In my case it was the Listening port conflict causing the issue. Listening port is used by the Communicator Web Access Server to listen for inbound communications from other OCS servers. We can check the current listening port from CWA console.
The conflict happens mostly when we add additional Virtual Server on same machine in scenarios where the Internal and External CWA Virtual servers are configured on same machine.
We can manually change listening port by updating “TrustedServiceListentingPort” WMI property using “wbemtest.exe” tool
WBEMTest.exe
MSFT_CWASiteSetting
Or
We can create new CWA Virtual Server and change Listening port 1025 through 65,535 by referring below article.
Creating a Communicator Web Access Virtual Server By Using the Command Line
More Info:
Preparing Certificates for Communicator Web Access
Appendix A: Ports Used by Communicator Web Access
Office Communicator Web Access Planning and Deployment Guide
