@David-l
I have my Race in DND all the time as I’m not interested in mobile notifications, it improves battery life massively & only takes a quick button press to wake up the watch to see the time (it continues to monitor 24hr HR/HRV).
I’ve found that if I wake up the watch with a button press & start an activity (DND still enabled in the background) the Race tracks the activity, gives HR zones/map etc & everything works perfectly BUT doesn’t vibrate even though its turned on.
I have to disable DND before starting the activity & then it vibrates as it should.
Took me a while to work this out as I’ve just started using the race nutrition app & kept missing the reminders.