New machine won't print

[cliffyk]

With the build plate assembly and resin vat removed, and "Home" button pressed, does the z-axis trolley fall, stop; and then rise and fall a bit before it stops? Does it do that with no grinding or growling of the stepper motor.

If so the limit switch is working as it should. When in that furthest downward position, with the platen lock screws loose, and a sheet of paper to protect the LCD glass is it possible to compress the platen against the preload spring and mount the build plate assembly onto the trolley arm? IF not the trolley has descended too far indicating that the limit switch is defective, improperly mounted or connected to the mobo, or maladjusted.

Yes with the plate removed and when I hit home it goes all the way down and rises a bit and back down a bit with no grinding. It also does this with the plate on and the screws loose but as soon as I level and tighten the screws it just bottoms out and makes that noise when it comes down.

Then platen must be shifting when you tighten the screws; try not tightening them as much, just "snug" them up. Do a test with something absurdly thick, like a piece of a beer carton, as a gauge.