1. 检查设备是否正确地注册了推送通知服务。可以使用以下代码：

import UIKit import UserNotifications

class AppDelegate: UIResponder, UIApplicationDelegate, UNUserNotificationCenterDelegate {

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
    //注册通知权限
    UNUserNotificationCenter.current().requestAuthorization(options: [.alert, .sound, .badge]) { (granted, error) in
        if granted {
            //如果用户允许了通知权限，就注册推送通知服务
            UIApplication.shared.registerForRemoteNotifications()
        }
        else {
            print("用户拒绝了通知权限")
        }
    }
    UNUserNotificationCenter.current().delegate = self
    return true
}

//注册推送通知服务成功后，APNS 会调用此方法
func application(_ application: UIApplication, didRegisterForRemoteNotificationsWithDeviceToken deviceToken: Data) {
    let tokenString = deviceToken.reduce("", { $0 + String(format: "%02X", $1) })
    print("设备注册成功，Device Token：\(tokenString)")
}

//注册推送通知服务失败后，APNS 会调用此方法
func application(_ application: UIApplication, didFailToRegisterForRemoteNotificationsWithError error: Error) {
    print("设备注册失败，Error：\(error.localizedDescription)")
}

//处理通知
func userNotificationCenter(_ center: UNUserNotificationCenter, didReceive response: UNNotificationResponse, withCompletionHandler completionHandler: @escaping () -> Void) {
    let userInfo = response.notification.request.content.userInfo
    print("didReceive response：\(userInfo)")
    completionHandler()
}

//处理在前台收到的通知
func userNotificationCenter(_ center: UNUserNotificationCenter, willPresent notification: UNNotification, withCompletionHandler completionHandler: @escaping (UNNotificationPresentationOptions) -> Void) {
    let userInfo = notification.request.content.userInfo
    print("willPresent notification：\(userInfo)")
    completionHandler([.alert, .sound, .badge])
}

}