I found the following in
https://devconnect.avaya.com/public/forum/d_forum_3.jsp?t=13140&f=44 :
The error message means that JTAPI did not receive the expected conf event from TSAPI for a request it sent.
Whenever JTAPI makes a request to AES (e.g. a CSTAMakeCall), the immediate response is in the form of a conf event (in this case CSTAMakeCallConfEvent). Every request without exception has a corresponding conf event. If a conf event is not recevied for a request within 1 minute, a TsapiPlatformException is thrown, with the error message you saw. Usually, this indicates a network issue which causes the conf event to be lost, although there might be other causes.
I suggest you check your network to make sure that thre are no problems there. It may also be useful to check the logs on the AE Services to see if they give any clues.
The thread also mentions that a problem in the application exposed a bug in the JTAPI client code. I suggest that you try using the latest (6.3) SDK to see if that clears up your problem. Also, check your code to make sure you are not using the JTAPI client improperly.
Martin