Turn on push notifications in the message centre of the Apple device. 

The firewall of the modem prevents connection with APNS (Apple Push Notification Server). 

Open listening ports on the router, see Apple's support site.

 https://support.apple.com/en-us/HT203609

If you have any additional questions, you can always contact us via this website. 

Please state the question or complaint clearly, so we can help you properly.