Short Version:
The “Override DND Mode” can’t be set via the app settings.
So you need to manually enable it in the system settings with tap on “More”.
Long Version:
Since Android 10 Google does not allow anymore that developers change the notification settings from the app.
Instead, the user need to go to the system settings and select for every app the notification settings.
The problem here is that you can’t set some special settings in the system settings like “Vibration Pattern” or the “Notification tone type” like “Alarm, Notification, Ringtone”.
We as developers only allowed to create and delete all settings, but can not change it.
So I added a workaround for this.
Some settings like “Vibration Pattern” are inside the app again.
After change, I read the current system settings for the notification and save it.
Now I delete all system settings and create a new one with the saved values except the changed ones from the users.
BUT the “Override DND mode” can’t be set from the app at all. Only system apps or the user can change this setting.
After recreation of the saved values I can’t recreate the “Override DND mode” and therefore this setting is again “off” if it was “on” before.
This has sadly to be done manually by the user. Because of this I added this warning message.