If you are running into a 404 Not Found error while attempting to use Replay (a feature used from ZT 5.5Z onwards) or trying to view live details in a local load test, you can resolve the issue by following the steps in this article. It is a matter of running the Windows System Tuning script in your ZT install folder, which expands the default set of ports ZT uses.

Cause of Issue: TCP sockets in use lead to 404 not found

If you examine the ZT console when you get this error you will see the following:

Basically the console is telling you that the ports used to handle the TCP socket connection are in use already.

Solution: run Windows Tuning file 

Navigate to ZT install directory and run the windows batch file called "WindowsTuning". For more information, see section entitled "1.3.2 Windows System Tuning" of the ZebraTester Installation Guide. This essentially expands the number of potential ports that ZebraTester can use. You may have to restart your computer, but first try to run the batch file and use the Replay function without restarting.

This should fix the issue. If you run the batch file, restart your machine, and the issue still persists, here are other workarounds that have worked in the past:
-upgrading the prxsniff.jar file to the latest .jar patch
-uninstalling and re-installing ZebraTester
These methods are not, however, guaranteed to work. 

If you try these solutions and are still having difficulty, put in a support ticket at support@apicasystems.com and the support team will assist you.