I have the same problem.
My filament sensor self test failed.
Rechecked all wiring, both cable ends colors sequence to pins are correct, white above on sensor and red to the outside in the main board bottom shelf. Tested cables for continuity, inspected the sensor for visible damage or debris, checked OK the 5A fuses.
I was careful to keep the sensor wrapped to protected it against static and I placed it using the wrap.
Sensor doesn't have a pilot light on, It would be nice miniature led.
This laser sensor uses the I2C protocol which is amazing, Red to black voltage has to be 5VDC to enable the sensor, and one 4.7kΩ pull up resistances to each SCL blue and SDA white ports (then from red port can be easily checked ) they are the communication and control I/O. Mine is a Rev. 0.2e
I am not receiving the 5VDC so probably the main board is defective.