nanoDLP

Mikhail As per Shahins post it does sound like a limit switch issue . The reason is this. When you power on a machine it has no way of knowing where an axis is until that axis has been homed so it will limit motion until it has homed and hit the limit switch at least once.   From what you have written it sounds like your limit switch is wired wrong or the logic in the software needs changing

At power on the z axis will only move towards home until it has been triggered once.

So you potentially have a couple of problems . Either your motor is working in reverse and /or you end stop logic is incorrect.
So we can use terminal commands to see whats going wrong .
So power off your machine then manually turn the Z axis until its about half way up its travel.
Send the M119 to find out the end stop status This will give you feedback on whether the end stop is triggered or not.
If you place an object in the lightbeam of the end stop it should read triggered and without the object it should be open.
If this doesnt work then either your endstop logic is incorrect or the end stop itself isnt working.
When you are confident the endstop is working then try this >>
Power on the machine but be ready to kill the power if needed.
In terminal send the Gcode command G28 The axis should move towards your end stop ( down) and stop when the end stop is reached.
If it doesnt you can either change the direction in the firmware or change the wiring of the stepper motor