It doesn't appear to be a problem with your camera settings. There seems to be a connection problem between the camera and the flash.
This might seem too obvious but make sure the flash is pushed fully into the hot shoe, as far as it can go. Sometimes there is resistance to further movement which makes you think it's fully seated when it isn't.
If you can, test the flashgun on another camera body, and test another flashgun on your body. This will help identify a fault with the flashgun or (less likely) the camera.