1) Before powering on the machine, ensure that the probe tip is straight (not bent) and can manually be pulled down and pushed up without any resistance.

3D printer touch probe sensor with red arrows showing movement direction

2) Next, turn the printer on and observe that the BL Touch probe deploys and retracts twice. If this behavior is not observed, proceed to the next step. 

Filament oozing from a 3D printer nozzle

3) If the probe does not deploy and retract when the machine is turned on, use the 2.5 Allen wrench included with your 3D printer to carefully remove the BLTouch and check that the wires are correctly seated on the back of the probe. Once completed, confirm that all the relevant BLTouch harnesses are correctly seated on the board.

BLTouch Smart V3.1 probe connector and wiring close-up
3D printer controller board with labeled wiring diagram and pinout connections
Mini-Rambo 3D printer control board wiring pinout diagram
8-bit 3D printer controller board wiring diagram with endstops, fans, hotend, heated bed, and fuses
BTT SKR V1.4 Turbo control board wiring diagram for power, heaters, fans, endstops, and BLTouch

4) Once the harness connections on the probe and the board have been checked, turn the machine on and observe that the probe deploys and retracts twice. If not, proceed to step 5.

5) Once you have confirmed that all the harnesses are seated correctly and the probe does not behave as described, use a multimeter to ensure continuity along each wire or contact Technical Support at MatterHackers (tech@matterhackers.com).