If the red dot guider is gone, check if the "red dot" parameter is set to 4.  For LightBurn users, enable "blanking".

If the red dot is still not showing up, check the input voltage of the red light guider.

1. Remove the cover on the horizontal arm.
2. Identify the line for the red light guiders inside the corrugated pipe.
3. Measure the voltage of the line. The normal reading is 5V.

• If the voltage reads different, replace the main board with a new, identical one.
• If the voltage reads normal, replace the red light guiders with new, identical ones.