Currently Alarmify works only if it is connected to a mobile network or WiFi. This is specified in the description of Alarmify in your App Store.
We are working so that this is not a limitation. From our next update 3.8.3 you'll start enjoying Offline options!
You can still keep Do Not Disturb activated, the alarm will not be affected by this.
How can I choose my music?
Do I need to have Spotify Premium?