Check to make sure that your camera doesn’t have an “auto-off” or “standby” setting enabled. This can cause the camera to shut itself down if there is no activity for a set period of time, especially if there is no activity (zooming, focusing, changing settings, and so on).
Make sure that there are no other settings that could prevent the camera from passing a signal through the HDMI cable and into the SlingStudio device. For example, some cameras have display settings that can include shutting off, or blanking, the display. This can prevent an image from being transmitted from the camera.
Some cameras may require you to put the camera in recording mode to prevent it from going into auto-off or standby mode.
Finally, try doing some basic troubleshooting: