If the screen shows only a generic Marlin date stamp, you likely have a very early release.
: Stock firmware often has the extruder cooling fan mismapped, meaning it only runs when motors are active. Updated configurations ensure it runs whenever the hotend is hot, preventing heat creep. sunlu t3 firmware
Invert the endstop logic. Open your firmware Configuration.h and look for X_MIN_ENDSTOP_INVERTING . Set it to false if it is true (or vice versa). You may need to recompile. If the screen shows only a generic Marlin