I have a question about my 504G. It will not complete post. When plugged into POE it starts, the Mute, headset & speaker lights come on. Then the display comes on as well as the Line keys. The line keys are orange and go out after 10-15 seconds and the display stays on with nothing displayed. This is as far as the unit goes. All I can do is plug it in over and over. Results are the same.