Hello dot.tom. Now, what I will suggest is to check the thermocouple of the left extruder of the heater. If you are able to find the heater embedded in the left extruder and on top of the left extruder nozzle, you will find the thermocouple embedded in the left extruder and on top of the left extruder nozzle as well, which is located right beside the heater. The thermocouple, without wires, has the shape of a hexagonal screw. You can then check if the thermocouple is working properly. If the control unit does not read the temperature through the thermocouple, the heater/hotend will not heat up. If you are not able to find the thermocouple at the left extruder, or if you don't know how to check if the thermocouple is working properly, let me know and I will tell you what to do then.
Good luck!
3d_Printer_Worker
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