"Needs Repair Error Code 6" means that the "high voltage power supply for the magnetron is out of spec."
The voltage could be too high, too low, or missing altogether.
Check the wiring and connections to ensure everything is securely attached.
Ensure there is no water or moisture inside the unit that could cause corrosion of the circuit boards.
Then measure the voltage to find out what it is reading, and we can go from there...