The signal strength LEDs can also be used as a time indicator for holding the reset button. When you press and hold the reset button, you have to hold it pressed for 5 seconds (by default) to initiate a factory reset. Each second, a new signal strength LED lights up. When all 5 LEDs are lit up, it represents that 5 seconds have passed since you pressed down on the reset button and that you can release it.
After releasing the button, all 5 LEDs will start blinking every 1 second. This signifies that the router has begun the factory reset.
We have one unit that starts flashing exactly as described above, only it never stops flashing, and will not function after a power cycle. Is it hosed? Is there something else to try?