During certain installation steps of the Door Keeper or its accessories, the Door Keeper's LED should flash. If it does not, there are two tests to verify:
1 / Remove and reinsert the Door Keeper battery from its holder.
If, despite this action, the LED still does not flash, you should check the battery.
2 / Verify the battery level of the Door Keeper. Remove it from the Door Keeper, then charge it. After that, you can reinsert it into the Door Keeper.