I’ve set a schedule as I always have done (on LineageOS android version previously) - on fairphone 5 fairphone os - nothing happens when its supposed to. do not disturb is NOT being enabled - even when schedules are there 
Any idea whats broken or how to fix it?
Did you confirm that the set weekdays & times are right, that it is enabled and that you picked the right behavior? I am on the latest iodeOS (LOS based) and it works perfectly fine for me.
Yes.
they are supposed to set dnd at 2200 and disable it at 0700 on weekdays and disable it on 0900 in weekends
Sounds like a bug to me, I would report it to Fairphone-Support.
