Hello,
What could be the possible reason for the following failure to connect. This a log from CTI engine. I have verified the usr/pwd. Tsapi client works fine. Tstest application was able to make successful call as well. CTI user has unrestricted access.

18:55:59:886471 LOW [123079536] src/TSAPIMsgMgr.cpp[401] connectAES:Trying to open Primary link[AVAYA#SDFG#CSTA#SDFH] user name[opencti]. Status=0
18:55:59:999986 LOW [123079536] src/TSAPIInterface.cpp[581] getAESMessage:CTIInvokeID/McrID[1010] TSAPIMessage[113:CE_MSG_TSAPI_STREAM_OPEN_CONF:TSAPI Stream Open Confirmation].
18:56:00:000188 LOW [123079536] src/TSAPIInterface.cpp[581] getAESMessage:CTIInvokeID/McrID[1011] TSAPIMessage[116:CE_MSG_TSAPI_STREAM_FAILURE_CONF:TSAPI Stream Failure Confirmation].
18:56:00:000601 LOW [123079536] src/TSAPIMsgMgr.cpp[618] connectAESHelper:Request Privileges conf failed.

Thanks in advance.

This looks like an Avaya product, such as Elite Multichannel, failing to get access to privileged features. In this case, you should open a Service request with Avaya Client Services.

<edit> I've just noticed that it is using the unsecire Tlink. It needs to use the secure Tlink[AVAYA#SDFG#CSTA-S#SDFH] to get privileged features.

Martin