The apps that ignore DnD and just ring right through are Viber, Hangouts and possibly others (I don't have every calling app installed). Calls show up on the screen but are silent. The apps that behave correctly on my phone are Skype and Facebook Messenger. No app should be able to override the OS's settings. It looks like this is a per app setting, up to the developers to implement correctly, which is false in my opinion.

These are calls from contacts that are not starred and the issue persists even if you set it to accept calls from 'None'. If above fails, back up the messages on those apps, uninstall and reinstall.While notifications and messages work just fine in do not disturb (they are silent), calls ring right through which renders do not disturb useless. Settings > Connections > Data Usage > Data Saver > set to off. Settings > Device Care > Battery > tap three dots: Sleeping apps – need to turn off.Solved: No sound notification on Messenger, Viber. Repair Viber Push Notification Problem Iphone Troubleshooting ….Viber Review – Is This Instant Messenger Secure in 2022? | VPNpro.Viber Is Not Working on My iPhone? Check Fix Here – iMyFone.What is the difference of calling and ringing in Viber? – Quora.9 Best Ways to Fix WhatsApp Calls Not Ringing When Phone is Locked.Viber issue - can’t answer calls – HTC One S | Android Forums.Can’t see when someone is calling me on Messanger or Viber.Marshmallow, Priority only mode, Viber still rings with sound?.Viber doesn’t ring when screen is locked – Windows Central.

Viber Settings – Viber Support Knowledge Base.Viber no ringing sound and notification – YouTube.

Solved: No sound notification on Messenger, Viber.

Viber messenger no ring sound