It may due to APNS expiration or incorrect

1. Please go to “Apple” > “APNS” > “APNS Info”
2. Check if the current certificate is expired.  If yes, please follow the instructions to update
3. If no, please go to “Device” > “Device Management”
4. Tap on the “Device Name” which is disconnected
5. In Device Detail page, scroll down to “APNS Cert UID”
6. If there is a notification of APNS is incorrect, please copy the last part of the UID (should be a mix of characters and numerics)
7. Go to https://identity.apple.com/pushcert to find the certificate matching the last part of the device UID. Download that certificate and update to ESP again