The Eyelights has not been designed to work optimally in underground parking or tunnels. Indeed, the device possess a brightness sensor that adapts to the light it captures. In the case of an underground parking or a tunnel, light variations due to lightning and low ambient light may give the impression that the device is flashing.
This is normal because the variations in light intensity are too quick.
The display can also turn off if you do not have enough network connection.
The Eyelights device will display your phone's screen again as soon as you will be out or have a connection back.