Why doesn't my iPhone ring with incoming calls when using apps?

For months my phone doesn’t ring with incoming calls if I’m using an app. At first it seemed to be one or two games but it has spread to all games and now Kindle. Generally, it will send the call to voicemail but sometimes the caller gets nothing. I’ve tried all of the suggestions I can find but no luck. Finally I bought a new 16e and downloaded everything from the cloud. That was 3 days ago and the problem remains. It’s so irritating that my phone doesn’t work.

[Re-Titled by Moderator]

Original Title: iphone doesn’t ring