I am not a DaVinci user, but it sounds like:
1) LCD connector to the board are loose/have a broken wire
2) The LCD is busted
3) The LCD is functional, but the backlight is way down to the point you cannot see the controls
4) The firmware on the board itself is fudged (most likely)
Can you control or move an axis?
Your post makes us suspect that it used to work, but no longer does, which would be a board problem if you have replaced the screen and wires.
Can you elaborate? Please be specific as every detail may count.
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