If your application isn't working, go through this checklist to make sure you've covered these bases:
Is the Communication Server running and accessible by your workstation? (Can you run the example applications and log in to the Administration Console?)
Check your spelling. Ensure that the PeopleList component has an instance name (in its Property panel) of peopleList_mc and the ConnectionLight has a name of connectionLight_mc.
Ensure both of the instance names are registered with the SimpleConnect, Flash Communication Components parameter in the Properties panel.
Are you accessing your Communication Server properly in the SimpleConnect? If you are accessing the server locally on your computer, use rtmp:/myFirstApp/; remotely, use rtmp://192.168.0.2/myFirstApp/. The IP address should be the IP address of the server that is running Communication Server.
Does your main.asc file have the command load("components.asc");? Server code is case sensitive, so make sure this entire command is lowercase. If you changed the file, did you restart the server?
If you are still having problems, step through the exercise again slowly.