Android 7.1 / 8 and Iphone X IOS12 can't get notification on mobile desktop

Hi RocketChat
Here I got some problem on my RC server. The Server version is 0.69.2 and I have test tow clients， one is Nexus6 on Android 7.1
the other is iphone6 on IOS11.3 .

1. The iphone6 connect to server can get notification when the app run in backgroud But the Nexus6 can't (no notification on mobile desktop)
   and I have already open all the privileges on Nexus6 for rocketchat app。
2. More test ，Iphone X on IOS12 also can't get notification when it run in background(all the privileges have been open for it)
3. what't the notifaction port when Rocketchat work ？ My webserver use Apache reverse proxy to proxy the port 3000 ,
   and I vist it such as https://xxx.xxx.xxx:8888 (8888 proxy the 3000 )，so I just open the port 8888 on my iptables ，is there more port I need to open？

Thank you for your answer.

No source files, tests, or entry points are named. Start by reproducing the notification failure with Rocket.Chat 0.69.2 on the listed Android and iOS clients, then inspect the Apache reverse-proxy and port configuration. Done means identifying whether the failure is client-specific or proxy-related and documenting a verified notification setup.