Please be sure to follow this guide:
How to re-stream video from an IP camera (RTSP/RTP re-streaming)
If the camera is setup to require authentication you can add the username and password to the URL in the .stream file like this:
Also, you can check the logs for any errors or warnings to see if you can track down the issue. To start Wowza in stand alone mode, and view the output in the console use [install-dir]/bin/startup.bat
This guide aids in troubleshooting:
How to troubleshoot RTSP/RTP playback
I hope this helps.