If your base station’s light is flashing
The table below describes status light behavior for the AirPort Extreme, AirPort Express, and AirPort Time Capsule.
The base station is unplugged.
The base station is starting up.
The base station can’t establish a connection to the network or the Internet, or is encountering a problem. A red badge may appear to provide more information. (See below.)
Solid or flashing green
The base station is on and working properly.
Flashing amber and green
There may be a problem starting up. The base station will restart and try again.
If a red badge appears near a base station: A status message is available. Click the base station to view the status message.
See the Apple Support article AirPort base stations: About AirPort base station status lights (LED).