We also have continious problems with PUSH notifications. Some Android OS receives other OS don’t, same with iOS, some iOS receive the PUSH perfectly in top of screen, others only when opening the PUSH feature in the app itself.
Also after the last Siberian update, some apps on iOS shown only a spinning wheel after opening the Push feature in the App.
@khurram, please have a look at the developers page of iOS and look if all certificates are correct and active. Otherwise revoke all and do it again from scratch.
And try to ask other people with different OS and different settings.. We experience also a lot of trouble with Wifi, so make sure that’s also switched off!