Try a camera reset.
You may have inadvertently set something that is causing the problem.
Look in the Index at the back of the User Manual.
Look for "Reset All"
See if the reset cures the problem.
When I attach the Canon AV cable (the one that came with the camera) from the camera to an ordinary TV, the camera image appears momentarily on the TV - with the LCD blank - but then the LCD comes on and the image on the TV disappears. Does anyone have an explanation?