When using the myPortal to Go app on iPhone it is very important that the network is properly configured, especially when the app is running in the background. This is necessary since we need to use APNS for VoIP calls. The Apple push notification service (APNS) is used to inform the user about incoming VoIP calls when the app is not in foreground

As long as the iPhone is unlocked and the app runs in foreground, incoming VoIP calls are signaled via the direct network connection from OSBiz to the app.

APNS notifications are only used in background / screen lock / screen off mode, where the operating system prevents myPortal to go (iOS) from running in the background. APNS means that the OSBiz sends call notifications to Apples public push notification service, which forwards the notifications to the corresponding iOS device. Here, they are handled by the operating system (not by the app), showing the call notification popup and playing a notification tone - which is the Unify ringtone in our case.
Clicking / swiping that iOS notification starts myPortal to go again and brings it to foreground, where the ringing call is detected, presented and where it can be answered.

To get the APNS mechanism working, the following administration steps are required:

1. The latest myPortal to go (iOS) version from App Store needs to be installed.
2. Please make sure that the app has all required permissions (iOS settings -> apps section -> myPortal to go).
3. In OpenScape Business, we recommend to use the latest V2R4.1 software release.
4. OpenScape Business (and Booster Card/Server if present) require internet access, as they need to be able to send notifications to Apple's public APNS service.
   This requires also a proper DNS server configuration, which allows OSBiz to resolve public internet domain names like "gateway.push.apple.com".
5. Both OpenScape Business and the iOS app need direct (proxy-less) internet access to the apple servers.
6. If the company firewall restricts outbound internet access, then please make sure that the firewall is open for APNS related ports. For details see here:  https://support.apple.com/en-us/HT203609 
7. The iOS device obviously needs an active internet connection (WiFi or mobile data) to receive and handle APNS notifications.

Regarding WiFi availability when the iPhone is locked:
Please check if specific power saving settings are in use. For example, the iOS option "Low Power Mode" may have an impact if enabled, especially when the device's battery status is low.

Lastly, we have seen blocking situations in iOS regarding APNS in rare cases which required a device restart to overcome.

Final remark: All hints above are related to iOS only.

See also: http://wiki.unify.com/wiki/myPortal_to_gohttp://wiki.unify.com/wiki/myPortal_to_go