I have a fairly new swing away heat press. It was working fine except the swing arm was stuck. My husband took the swing away part off and fixed it. But now when I plug it in it shows E3. I was told by the seller what it could be... either the wire from the control box isnt connected to the plate OR an open circut fault of the thermocouple. We have looked at this.. but can't seem to find anything wrong. Any ideas on how to go about fixing this??