BIQU Thunder extruder problem

Good Morning

I have a BIQU Thunder and the extruder will not work. I have waited for the temperature to reach 180 and still nothing. I have tested the cables using known working cables, still no luck. I have tested using a known working driver, still no luck. I have tested by plugging the y axis cable into the extruder and I can control the extruder using the y axis controls so I know the extruder itself and motor are fine.

I have come to the conclusion that it must be the port on the control board is faulty. I do have a second port on the control board but I understand I need to edit the firmware to use this. Does anyone know how I can get into the firmware to edit, I know what I need to do once in, I just cannot work out how to get into the firmware to edit.

Thanks

Kevin