I have tried every solution suggested, and still my iPhone app will not ring if it’s not in the foreground. I’m using an iPhone 7 Plus, I have checked all notification settings, I have turned background refresh on, and nothing works.

If I uninstall and reinstall the app, it will work for a little while, and then it stops.
when doing some research as though I were a developer, I noticed that iOS 13 made some significant changes to the way it handles VoIP calls in the background. I’m wondering if RingCentral has made all the required changes to be in compliance with Apple’s iOS.