You can't tell they are faulty just by looking at them. You need to try them in another device, phone, hifi, tablet, pc etc.
If they are ok on another device, then you almost certainly have a defective input socket on your YPT-210. Try another pair of phones in it. Even a cheap supermarket pair will tell you immediately if it's working properly or not.
If not, then a wire has probably broken or come loose between the headphone plug and the side of the headphone that has no sound. If the plug unscrews then check it out first. You may need to resolder the connection/s. Doesn't matter how pro the headphones are.... They break. Nothing is perfect.
I've got a set of headphones I've had for 20 years plus. £10 new they cost me. They've outlasted several Pro ones.