How to solve MIUI phone do not have notification sound issue?
In fact,it's a known issue of MIUI phone ,you have to enable "sound" option at phone system settings->apps->Next SMS->notification . Open each channel , and then enable "sound" option . but when you change notification sound /vibrate setting ,you need to enable them again. It's limitation of MIUI phone ONLY . none of other brand phone need to setup manually.
If you are always using default sound you don't need to setup sound individually ,enable "sound" option at channel is enough ,and you just need to setup once . If you custom sound often ,we have a solution to resolve the issue, you just need to install Notification plugin app from handcent settings->Notification plugin ,then active it . after done ,just "lock" notification plugin app from task manager of MIUI (don't kill the plugin when clear memory) . after done these ,sound will always on,you don't need to setup manually anymore .