Unable to recieve SIP calls when app is in background

Question

I am working on an iOS app that uses push notifications to wake up the app so I can receive SIP calls when app is not in foreground. When all is working, app gets a VOIP push notification while in background which wakes up the app and within 5 seconds I get a SIP invite to process the call. We are using a timer for 5 seconds to wait for SIP after getting VOIP push. The issue I am having is after a certain period of running sip calls test, app stopped receiving SIP invites if it is in background. This happened on our multiple test devices. Restarting the app and rebooting the device didn’t help but uninstalling & installing the same version of app did the trick. What could be the reasons behind this and how can we fix this? Have anyone else experienced the similar thing? Any suggestions . TIA.

Answer 1

Could it be related to SIP registration process, you need to register to sip before get invite, registration process may take more than 5 sec bcs of network conditions.

If I were you I would check SIP registration process first and make sure I got 200 from SIP before Invite process.

Answer 2

As far as I know, Apple bans application in iOS 13 or higher, if there is no connection to the SIP-server, when you receive a push.

They regard this case as an incorrect use of VoIP-pushes and write some blocking record to your app. When you reinstall it, this record disappears and you can repeat the same thing.