Light Flow only controls the one central LED on the illumination bar, can it control all 3?
Yes it's possible to control all 3. Go into lightflow -> settings -> Led Control
Switch off "Main LED Control" and switch on "Illumination bar"
Then for each notification lightflow will use the new illumination bar option instead of the default color setting. This option allows for all three leds to be on and also allows for control when the screen is off.
The led does not work, what can you suggest?
Firstly make sure stamina mode (or extended battery mode) is disabled as this will kill any 3rd party services running in the background (including light flow)
Go into your phone settings->accessibility and switch off and back on lightflow in the list.
Check if there's a setting in your phone settings->display. If there's one regarding the led/light make sure it's on. (don't worry if it's not there)
Switch off your phone with the power button. Then switch it on again.
Go into lightflow -> general settings and make sure direct mode is off.
Then go into notifications -> missed calls.
Set the color to "red"
Set the flash speed to "fast"
Switch off your screen and wait 10 seconds.
Does the LED light up?
If that doesn't work, can you go into your phone settings, apps, choose lightflow and select "clear data" and see if that helps.