It sounds like you have two problems. One with the headphones and one with one of your cables.
First - sound in one ear only is probably that the connection between the jack and headphone speaker is open. Either lack of tension in the spring connector in the jack itself where it touches the plug - (gently try to move plug side to side / up and down whilst inserted in jack and listen for sound in speaker side not working), wire off jack terminal, wire broken between jack and speaker, wire off speaker terminal or faulty speaker. The convention is/was that the "tip" of the plug connected to the left speaker and the "ring" (next connection on plug) connected to the right speaker and the "sleeve" was the common (or earth or return) for both speakers. But sometimes manufacturers do whatever they want.
You will have to open the headphones up and using an ohmmeter do a point to point test of the wiring path to locate where the problem is.
Next - the cable that gave no sound could have a faulty connection say for the tip (left speaker) and if the headphones had a faulty connection for the right speaker then you would end up with no sound in either ear, which I think you said happened. Of course it could be the other way around or it could be a faulty "sleeve" connection in the cable as well. You could try inserting this cable and the gently flexing it just past the plug at either end of the cable and listen for any sounds. This may tell you where the problem is if the wire has just come loose in the plug. Then again you may not hear anything.
Hopefully this has been of some help
Hi @ BeeBoy1 The Gamer,
It may be that the cable socket in the headphones or a connection to the socket is the problem. It could also be a problem in the BT chip or from the BT chip to the socket but hopefully not
Don’t know your headphones but they may use a headphone socket that physically changes the connection over from the BT to the cable when you plug the cable in.
This image is an example of what I mean. (to my knowledge it is not the socket used in your headphones.
Click on image to enlarge for better viewing).
The BT left speaker output would be on pin 7 and the left speaker amp in is on pin 6.
The BT right speaker output would be on pin 3 and the right speaker amp in is on pin 2.
When you plug in a cable, the connection between pin 6 & 7 and pin 2 & 3 is broken and the cable input is connected to pins 2 & 6 for the left and right speaker amp inputs, thereby changing the amp inputs from the BT to the cable.
This is an EXAMPLE ONLY to show you how it MIGHT be wired in your headset. Depending on which speaker has the problem (L or R) it could mean that there is a faulty connection on pin 7 or 3 (depending) or that the contacts are faulty. The contacts are internal to the socket so the whole socket would have to be replaced. You could test the contacts for continuity by using an Ohmmeter but this would mean that you’d have to open the headset to gain access to the board where the socket was mounted.
Again this is just to show you how it MIGHT be wired. No doubt the socket in your headphones would not have as many contacts as the example shown. Possibly it would only have the 2 “break” sets of contacts.