I recently unplugged my M4 system which i have lived and have had zero issues with over the past two years. I set up the main unit with no issues then set up my second unit. It keeps blinking blue like it's connecting but doesn't connect. I've tried resetting and unplugging. I've put right next to the main unit but they aren't 'talking'  I have held the reset button multiple times for multiple different lengths of time and plugged and unplugged it multiple times. Any ideas would be greatly appreciated.