Have checked the cables over and over again and I find it correct.
The LCD starts and the backlight shows, but not the letters.Sometimes the white boxes flashes a millisec or so, then disappears.
I got the 10K potentiometer. And I have tried with and without it, same result.I also cant change the contrast with the potentiometer coupled on.
Ive checked the outputvoltage on it,and it works!
We really can't give more help without more information.