I recently installed a KX-TVA50 on an existing KX-TD 816. I checked the Message Waiting light option in the TVA 50 windows software but they dont light. Under program 005 in the 816 I programmed the button as "3". Any suggestions as to how I can get this key to light when there is a message, do I need to enter a light on and light off sequence in the TVA 50? Hope you can help