I would take the top off, check for voltage at the motor and work my way back to the control board. There are plenty of exposed/semi exposed mains voltage connections and this test needs to be done live so only tackle it if you are competant/your own risk, etc, etc....
You could also check connections with the power off before live testing.
If you check the clarke website there should be a manual with a wiring diagram.
Have you tried for wire feed at all settings of the power selection switches?
The supply for the wirefeed motor is taken from the main welding output. Even with no movement of the wire, can you still strike an arc at the tip of the MIG wire?