Take me through the process of what you do when attempting the glitch and I'll do my best to pinpoint what the issue is as well as tell you a fix for it.

Make sure you have your timing right and you are pressing the correct buttons.

OK I get rid of all the other junk and just keep a copper in my inventory I go across to the work bench and hit triangle then square it moves it across but then when I go back to the work bench the copper is back in my inventory and I still have the same amount

ALBA wrote OK I get rid of all the other junk and just keep a copper in my inventory I go across to the work bench and hit triangle then square it moves it across but then when I go back to the work bench the copper is back in my inventory and I still have the same amount

Make sure all junk is out of your workshop and inventory except for the shipment (in this case of copper) in your inventory. Go into the workshop and press triangle then square and if you did it correctly then the shipment will be back in your inventory as well as there will be copper in your workshop. If your shipment of copper is going back to your inventory, but not producing any copper in your workshop then you need to get a new shipment. I would also suggest saving/reloading your save before attempting it again. One of those if not both together will fix your problem unless it's just an issue of timing for pressing the 2 buttons on your end. Best of luck and I'm here to help any further if needed.