Apple SMS saw how to display unread.

Inbox is full, and some security software such as 360 intercepts or filters short messages.

1. Inbox is full: some short messages cannot be received normally. You can check the message option in your phone settings to see if you can't receive unread messages because your inbox is full. If this is the case, you can try to delete some unnecessary messages to make room for receiving new messages.

2. Some security software, such as 360, intercepts or filters short messages, which leads to these short messages not being received normally. You can check the security software settings of your mobile phone to confirm whether unread messages cannot be received due to interception or filtering. If this is the case, you can try to turn off or modify the shielding or filtering settings of security software so that these short messages can be received normally.