Could be the wire going to the earbud that’s broken or it could be something on the circuit board that is broken. These kinda repairs are tricky and in the end they probably won’t look as good.
You could attempt to repair it if you are willing to break the entire thing.[br]
If you can get the thing apart i would start with measuring the resistance between the wires going to the earbud, I think the measured value should be pretty low, 4-16 ohms low ish.