Not sure if anyone faced this issue before,i'm on ROM MIUI 8 Global 6.8.11 Beta.
Apparently there's an issue with the AUX output,the headphones which i used to plug in,is not working. the sound instead is output through the phone's speaker.
swap another earphone,same issue.
Both the earphone is tested on another device and is working properly.
Did a quick search and found out that i'm not alone. Hope they will fix this soon.
I managed to find a workaround,i half plug the headphone jack into the port,then launch the music app,play it,then fully plug into the jack.
If i plug it in directly,the sound will come out from the speaker,the headset icon on top will disappear,sometimes after unplugging it,then icon will still be there.
Did a test on CIT,and it detects my headset as plugged it even though i removed it already.
I have this issue on miui 7 latest stable rom too.