1. The filament has not entered the Teflon tube. Please manually load the filament into the Teflon tube.
2. There is a certain distance between the filament from the cold end of the extruder to the hot end. The filament has just been loaded, please wait.
3. If it still cannot be extruded, check the distance between the hot end nozzle and the heated bed (when the nozzle is too close to the heated bed, the filament cannot be extruded from the nozzle).
4. If it still cannot be extruded, the nozzle may be clogged. Check the situation without loading the filament. If the extruder is working normally, the hot end is clogged and the hot end needs to be replaced.