When the disc screen is not lightening up, it means there is a connection issue between Disc and Lock itself.
Steps to fix it
Separate disc from the lock using tool
Separate battery and disc too
Check if all 4 little pins on the Disc are whole
Make sure the disc and battery is connected correctly (pins should be pointed on the battery little yellow part)
While putting the disc in the lock, make sure you push back it in one hard movement, So it will connect to the lock
Reset the Smart Lock (press and hold the button in the back of the lock).
Warning
The little button inside the lock should beep when you press it for several seconds to reset the lock.