BLTouch with TH3D Ender 3 pro I installed TH3D to my stock mainboard via this guide, but BLTouch does not work properly. 

It does not check all 9 points before point it just go middle then check z then start printing. BLTouch normally needs to check all 9 points before printing or with autobedleveling but somehow mine do not work like this.
After setting up the BLTouch in firmware, you need to activate the leveling function for every print by inserting the leveling G-code 'G29' in the start G-code script of your slicer. The code should be placed directly after command G28.

Note that you can test the working of the sensor from the printer display: sensor can be deployed, stowed, reset and tested.