I'm sorry if this answer is somewhere else on this forum, but I've searched for three hours and cannot find a solution. We have an Electra system, and I think it's a Pro II. Some of the phones ring on incoming calls and some don't. I've adjusted the ringing volume on the phones that won't ring by dialing 601 and using the arrows, but they still won't ring due to an incoming call. I've accessed the programming mode but can't find any relevant information there. DND is off. Any assistance would be greatly appreciated.