First test whether it is a software or hardware issue. Do this by connecting your bluetooth to a device then determine if both earphones play equally. If not, plug the aux cord from your device into your headphones. Plug the aux cord slowly into your headphones to see if it switches from audio playing on one side to playing on both. Check your settings to determine if your sound is getting equally distributed. If so, The Aux Jack-in could be damaged or dirty or it could have a bad connection. You may need to disassemble your headphones and fix the problem. Headphone bluetooth transmitters and aux Jack-in run parallel circuits with one another. So when we know that only one side works the problem can be shifted to the other side, to be dealt with. Look for a faulty aux cable, or worn out jack’s. That could cause a loose connection as well.