iOS pushKit pushRegistry:(PKPushRegistry *)registry didUpdatePushCredentials neverCall in Individual devices

Question

1. Is open
2. Capabilities -Push Notifications is Open
3. Background Mode : Voice over IP open backgroud fetch open Remote notifications open location updaete open; code : enter image description here

Delegate <PKPushRegistryDelegate> also observe but just some device (Especially small probability) never call didUpdatePushCredentials() mothod, I tested many times, (uninstall app, install app),it also never call this method, but when I restart device then method called, Has anyone ever been fall in this situation? Can anyone explain this?