A new digital Panasonic has been installed with 6 hunting CO's. Line 1 will not ring in the number one position of the system but it will ring in any other position. Any line connected to the number one position will not ring there. We have reset the system, reprogrammed ringing lines and even went back to Graybar 3 times for a new system. Line 1 will not ring no matter what!! Any ideas anybody?