3151509 - EPM connection issues when using "Web Authentication Protocol" option

• You have configured EPM Add-in connection to the server through a message server.  You expect for the users to get authenticated through “Web Authentication Protocol” option of the EPM Add-in.  However, the authentication fails.
• You have this issue only when connecting EPM Add-in, users have no problem connecting through BPC web portal.

EPM Add-in for BPC NW, All versions

dispatcher, web dispatcher, Web Authentication Protocol, System.Net.WebException, "The remote server returned an error: (401) Unauthorized", System.Runtime.Remoting.Proxies.RealProxy.HandleReturnMessage(IMessage reqMsg, IMessage retMsg)
System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData& msgData, Int32 type)
FPMXLClient.BPCProxy.Session.Interfaces.ISessionService.Logoff()
FPMXLClient.BPCProxy.Session.SessionServiceHelper.Logoff() at \src\FPMXLClient\src\BPCProxy\Session\SessionServiceHelper , KBA , EPM-XLS , EPM Excel Client , Problem