Earphones one side lost sound ?

Buy a new one, it's going to Damage.

There could be a broken wire on that side. There are some scenarios of a broken side of headphones that are easier to fix than others. I would suggest simply getting new ones

Usually earphones would blow.

This is a common thing, you likely won't be able to fix it but buy new ones

I don't know how to explain it, but you can press and bend the squishy part near the base of the wire to get it working again. It's usually just a cord issue.

that means the angel and devil on your shoulder were fighting and one of them just lost

You will need to figure out which part of the cord where the sound is cutting off, and bend it to get it working again. If you can't figure that out, bring them to an ERA and purchase a pair of headphones that allow you to use your own line/aux cable. Well worth the money.

Find the fault and correct it.

Broken wires are the most common cause.

They are sometimes Very difficult to repair.

Most of the time it's wire damage. Cord bends allot over time the wires inside cable split apart . Me i splice and solder replacement cords to repair the problem . YouTube videos how to do it . Buy cheap 3.5mm male to male cables cut them in half use them , must solder because wires are coated so won't work by just twisting them together .

Sound like you need new earphones.

plug it back in