The Window Unit status indicators may be Green Flashing (setup in progress), or Green solid (system working), Red (system fault), or Orange (external antenna connected and providing a stronger signal that internal antennas).
If you are using an external antenna and the indicator is not Orange, then either the antenna or its feed is faulty, or the internal antennas have a better signal.
Note that Cel-Fi was designed so in nearly all cases an external antenna is unnecessary. Also note that an Orange indicator looks a bit reddish so this might confuse some people. A true Red LED would indicate a Window Unit fault. If power cycling the Window Unit does not solve the problem, RMA the system.