What are the possible reasons to get APNs responses BadDeviceToken or Unregistered?
问题 When sending notifications to iOS users, for some of them I get response status code 400 (BadDeviceToken) or code 410 (Unregistered). From Apple documentation about "BadDeviceToken": The specified device token was bad. Verify that the request contains a valid token and that the token matches the environment. What is the meaning of "bad"? I know for a fact that the device token was valid at some earlier time. What does a user do to make its device token bad? From documentation about