After replacing the wired fire alarms in my house with new ones, when testing any of them, that one beeps but not the others.
Model is BRK First Alert 9120B6CP.
Each alarm came with three cables. Black and white for power, and orange for sending the signal that should cause all of them to go off when one of them does.
I have verified they are all properly wired and that they all have power (green light is on for all).
Any ideas on what else to check or verify to have them all communicate?