After replacing the nozzle, printer status indicates that extruder temperature is 300℃, and the fan is also working. Why is this happening?

Adventurer 4

Note that the temperature setting in the slicer file might not match the highest temperature of the replaced nozzle.
Errors in temperature displaying indicate that the new nozzle is not properly installed, and the extruder temperature cannot be read by the sensor. Please plug out and install the extruder again, make sure that the extruder is pushed to the end, and the buckle and bottom of extruder are on the same level. Refer to Q2

Note:Power off when replacing the nozzle