At the start of 2019, Hikvision will be introducing the new Hik-Connect App.
Hikvision Europe Technical support confirms that when a smartphone goes into idle mode, the Hik-Connect App does not receive a push notification.
The reason is that the current Hik-Connect version uses a push with general priority, this kind of push will be delayed to send when phone is in idle mode or the operating system of the phone has the App in energy-efficient mode to reduce energy consumption to save. In some situations, even the WiFi of the phone is turned off if the phone is not used for some time.
In conclusion, the problem is that no push notifications come through right now, mainly because SmartPhone manufacturers have adapted their firmware in such a way to extend the battery life that third-party products are now experiencing.
The good news is that Hikvision has indicated to us that in Q1 2019 it will come with version 3.7.x which will support the Keep-Live function, reducing the delay of alarm-push. This other way is high-priority alarm push, which allows the FCM service to wake the device out of idle mode and send the push.
Source: https://completebeveiliging.nl/blog/post/begin-2019-komt-hikvision-met-de-nieuwe-hik-connect-app.html