My 2 cents go on the fact that you probably have camera access denied from the Player global settings and the remember checkbox is selected. Listen for camera status and activity events and also check if you are allowing access to the camera an the camera is not in use by other app.
your reply is very helpful to the problem. thank u very much. now i insert some code such as trace(cam.muted), then debug log is "true", then i change the Player global settings to allow, but i still get the "cam.muted = true", "true" and "true". what shall i do? just getting another usb-camera to replace the one i'm using is the final resolution?
Not sure here, some customers complained that they cannot use the camera starting about 2-3 weeks ago. We haven;t been able to reproduce it internally so far. We found there is a bug inside flash player. Most people claim is happening only on MAC, however our user reported is on Windows. If you happen to be one of the people getting the bug than I really have no answer at this point.
Normally if the camera is in use by some other application it will be muted. Make sure it is not in use by any other up, Try with a different camera or also with some camera simulation software e.g. many cam or splitcam. However I experienced some issues with those in your past.
HTH in some way.