Can't change notification sounds from "default notification sound" to "none"

[yvmuell]

So you try to set per notification? Did you try to go through settings-sounds-advanced-notifications?

Maybe this thread can help, although reg ringtone

Custom music Ringtone does not work

Try turning “Do not disturb” ON and then OFF, and then restart the phone. This has helped with similar cases in the past. EDIT : just noticed in your screenshot: I think Do not disturb is on. Turn it off, then restart the phone.