Why does the Xiaomi Smart Band 9 Active fail to reply with text messages?

SMS reply failure is a result of the SMS reply process. It is not an unexpected problem and has nothing to do with the band. It is caused by the permissions granted to the Mi Fitness APP by the mobile phone or the incompatibility of the mobile phone system with the Mi Fitness APP.
To allow SMS permission, please refer to the following steps (take the Xiaomi smartphone as an example):
1. Go to [Settings] on your phone;
2. Scroll down and select [Apps];
3. Tap [Manage apps];
4. Find and select [Mi Fitness];
5. Select [App permissions];
6. Tap [SMS] to allow SMS access for the Mi Fitness APP.
Note:
The SMS quick reply function is only supported by the Android system. iOS phones do not support a SMS reply because the iOS system does not have permission to reply to SMS messages.