I'm using Zoiper on iOS and bought a Push Notification subscription.
However, I don't receive notifications on incoming calls when the app is closed for a while. Incoming calls work when the app is opened.
I know that background apps get terminated on iOS but I assume that at least I will receive a notification on incoming calls (which is not the case).
I'm using a SIP account and tried "SIP" and "SIP+RTP" for the Notifications.
Any ideas on how to get Push Notifications to work?