Why aren't my FOB lights coming on?

At times we may expect FOB lights to be on or we don't understand why they are not on. Below are some reasons the lights might not be on. 

New system set up. Fobs need to be set up and all software updates performed before lights will function.

Low battery voltage.

When replacing a battery, on a FOB that has been set up, the light will flash momentarily. We may miss seeing the lights flash as we have the FOB turned over during battery replacement.