i had the same problem but i found a way to fix mine. i took the speaker out and realized that one of the copper springs wasnt straight and it was bent to the side, and wasnt connected. so i straighten it out and made sure it was connected, i put everything back and it worked perfect.
https://d3nevzfk7ii3be.cloudfront.net/igi/IZYXyFLf3OoXZJSt.huge
if u look at the picture the one is his hand is the earpiece speakers, and to the left of it is two copper recievers? i believe is wat its called. they need to be fully connected for the sound to work
I hope I was of help.