QuickBlox iOS SDK supports VoIP notifications in the background/non-running state but the implementation of this functionality depends on application workflow and is up to the client-side.
For guidance on the implementation of VoIP notifications in the background/non-running state check the QuickBlox iOS WebRTC samples here: Video calling | code samples
You can find more information about how to subscribe and receive VoIP notifications in our documentation: Push Notifications | iOS SDK | QuickBlox
Please make sure that you have added an APNS certificate to your Dashboard: APNS | iOS SDK | QuickBlox
See these articles for further help on the implementation of VoIP functionality on the client side:
Feel free to check our official documentation for more information that will help you to integrate QuickBlox services into your applications / projects or contact our Support team by submitting a ticket if you have any other questions.