1) Please make sure the switch of the relevant settings of your device is turned on.
2) Please make sure the system notification permission of your phone is turned on.
For IOS users:
https://support.apple.com/en-us/HT
For Android users:
https://support.google.com/android/answer/9079661?hl=en
3) Check if there are any network problems, such as whether the hosts of the router have been modified.
4) Check if message settings are set for no-disturb, no push for events, no push for devices, etc.
5) Apple devices need to check whether the app is online in the background, and do not receive notification bar messages when the foreground is online. For Android devices, domestic manufacturers are not configured, so the app should always be hung at the front desk.