When you run the auto-level job, your CNC machine will move to the Start At position defined in the Pre-Run tab (typically X0 Y0) and then slowly descend on the Z axis until the Z Min Switch circuit is completed. You must make sure that your Z Min Switch is wired correctly and has minimal noise on the wiring. The TinyG does seem extra sensitive to noise. It can help to twist your wires, like the way ethernet is twisted, up to the point where you need to connect one wire to the PCB and the other to the end mill.
The first point probed (the Start At position) will become your default Z0 position. A G28.2 Z0 command is issued after the first probe to set that as your Z0. All other probe locations are offsets of the first position.
It can help to run a test probe to make sure your Z Min Switch wiring is correct. When you click "run test probe" the command G38.2 Z-10 F5 is sent to the CNC controller. This will start moving your Z axis down very slowly at a 5 mm/min feedrate. You must have your wires connected correctly, or you could manually choose to touch your end mill wire (alligator clip) to the PCB board well before the Z axis reaches the PCB just to test that the G28.2 command stops the moment the circuit is completed.
The Z-10 in the command just means your Z axis will move down a maxium of 10mm before it gives up. You should make sure that you have your Z axis set such that the Z-10 gets far enough to actually touch the PCB if you want to do a true test of the end mill making electrical contact with the PCB.
Get ready on your E-Stop button in case your circuit does not complete. You can also use the red stop button in the TinyG widget to cancel the G38.2 command. That red stop button jumps ahead of any command and pauses the TinyG immediately. It works very well. Make sure to reset the TinyG planner buffer by hitting the % button afterwards.
During the probe process the matrix updates itself with the warpage. You can adjust the exaggeration of the warpage from the pulldown menu in the top toolbar.
You can do this from the upper right menu for this widget. Data is automatically saved into your recent file list after the probe process is done running.
You can do this from the upper right menu as well.