This article provides an overview of the LED states.
INSTRUCTIONS & INFO
When the LED is blinking slowly (every 5 seconds): BLUE LED: the AT&T network service is connected and the Main Wi-Fi network is enabled. AMBER LED: the AT&T network service is disconnected or the Main Wi-Fi network is disabled.
When the LED is blinking quickly (double-blink) BLUE LED: the device is transferring data.
When the LED is alternating a fast BLUE and AMBER blink: The device firmware is being updated.