Make sure you have entered the public IP address of your camera into the URL field on the Webcam Setup page of My EarthCam. If you have entered an IP address that resembles either of the following, you have not entered a public IP.

10.0.0.0 - 10.255.255.255
172.16.0.0 - 172.31.255.255
192.168.0.0 - 192.168.255.255

If you are unsure of your camera's public IP address you can go to http://www.ipaddressworld.com/ to try and find out. If you are still having problems, send a help request.