I recently bought a touch screen, I use Arduino and the screen, I have no problem with the code, but when they are connected together, I tap the screen and nothing happens.
The screen is from: https://www.stoneitech.com/
and the Arduino is UNO.
Since you have bought their LCD display product and you are having questions using it, I think you would be better off seeking help on their forum at https://forum.stoneitech.com
Besides, you did not indicate which exact LCD display model that you are using.
Sorry for the late reply, I think the advice you gave is right, I think the interface I am using is wrong, my LCD defaults to RS232 interface, I should change it to TTL interface.