The LED above the reset button on the processor, indicates whether your Lines are connected to WiFi or not. The four states of the power button LED are described below:
Steady On: This indicates that the Lines are not connected to a WiFi network and are searching for a network.
Off: This indicates that the Lines were able to successfully connect to a WiFi network (the Light Lines will also flash to indicate that they were able to connect).
Flashing (every ~1s): This indicates that the Lines has timed out and were not connected to a WiFi network within 30 minutes of being connected to power. To resolve this, unplug power supply from power and plug back in. After the boot up, the LED will change to On.
Flashing (every ~4s): This indicates that the Lines were connected to a WiFi network, but are unable to reconnect. Generally this occurs if settings on your router or WiFi have changed. To resolve this, perform a soft reset, delete any previous pairings from the Nanoleaf App and setup again.