Lenovo AIO S500Z PC touchscreen just work in the above left?

I have a problem with my touchscreen PC AIO S500Z. The touchscreen works, and the software has no issues. However, when I tried to calibrate the touchscreen, I found that it only responds to touch at one point in the top-left corner of the screen. The touchscreen does not work at any other points. What should I do? The screen does not have any cracks or scratches.