Camera won't work!

[HtC3d]

I tried everything! I press the button so that I can take a picture but all that comes up is the black screen with the camera icon then it cancells itself out going back to the home screen. I already restarted the phone and let it rest up to 30 minutes but when I turn it back on its that same, and all the apps say the same thing that the camera isn't available. Please I need some feed back on this any ideas on what I should do?