First try turning your Chromebook off and back on again. If this doesn’t fix the camera, try using the camera in a different app, like Camera, Canvas, or Zoom. If it works in one, but not the other, this will narrow down the source of the problem. If the camera still has issues, then reset your Chromebook: Hold the Power button until the Chromebook turns off, then press the Power and Refresh buttons at the same time to reboot and reset the computer.