Using deco M4 for over a year, they work well. But recently, all units turned red. I restarted the main unit and it works now.  I tried to connect the 2nd and 3rd unit at another location in my house. I plugged in the power and the unit showed yellow light at the beginning and then turned into blinking red. I also press the reset button under the unit but it didn't turn yellow light and keep blinking red.

Please advise.