"ErrorNoApplicableProxyCASServersAvailable" Problem

Hi everyone,

We have a standalone Exchange 2010 SP3 RollUpdate 2 server. We have very strange problem on this server. When we are trying to connect EWS services we are getting this error:

"ErrorNoApplicableProxyCASServersAvailable: Exchange Web Services are not currently available for this request because there are no available Client Access Services Servers in the target AD Site."

Test-WebServicesConnectivity and ExBPA results are success. We couldn't find a solution?

Some times, we are getting this event log.

"Event ID: 16 Client Access server CASSERVER failed to proxy Exchange Web Services to Active Directory site CN=Default-First-Site-Name,CN=Sites,CN=Configuration,DC=XXX,DC=com because there are no applicable Client Access servers in the destination site. Please check the configuration of the servers in site [No Server]."

http://www.ceyhunkirmizitas.net/microsoft/exchange-server/event-id-16-client-access-server-failed-to-proxy-exchange-web-services-to-active-directory-site/

Your help will be appreciated.

Thank you.