Check the Machine Settings in your software (e.g., LightBurn).
In the Z axis settings section, check if the Limit Trigger is disabled. If it is, re-enable it.

If the light inside the sensor is red, it means the sensor is constantly triggered. This will cause the Z-axis to keep moving up until it stalls at the maximum height.

Gently press the nozzle by hand to ensure it is retractable (it contains a spring structure).
Regularly clean the nozzle and sensor to prevent debris and grease from jamming the sensor:
Open the laser head box. Inspect the auto-focus sensor and its connecting wires for any signs of melting, shorting, burning, or breakage.

If you cannot visually determine if the limit switch or sensor is faulty, open the Diagnose page on the controller or software.
Manually press the laser nozzle or the sensor, and the Z-axis upper limit switch.
Observe whether the corresponding Z- and Z+ buttons on the Diagnose page change from green to red. If there is no change, the switch or sensor may be damaged.

Important Reminder:
If these steps do not resolve the issue, please click this link to submit a support ticket: https://zohodesk.1laser.com/portal/en/newticket. A technician will then be able to conduct a more in-depth diagnosis and resolve your problem.