Check the following
- Confirm that the HDMI cable is firmly connected to the camera body and clip-on LCD monitor.
- Disconnect and reconnect the HDMI cable to see if there is an improvement.
If you have other HDMI cables, try a different cable.
- Connect the camera to other HDMI support monitors and check that video and audio can be played back without problem.
If the video and audio are not played back on other monitors, check the HDMI output settings, etc., on the camera.