If you disconnect all connections, except Vdd (5V), Vss (GND) and Vo (Contrast), power the device up and adjust the pot attached to the Vo (Contrast), can you see a single row of black boxes across the top line?
As I mentioned, you may need to adjust the pot connected to the Vo (Contrast).
If so the device appears to be powering up correctly and is waiting for proper initialization.
Therefore as mrflibble has indicated you most likely have a faulty connection, probably on one or more data lines.
However, if the row of black boxes are not solid, some pixels on, some off, then you most likely have a damaged LCD.
Without seeing a picture of the display in question powered up it is hard to tell. It could be as simple as the contrast control not being set correctly.
Connect the pot between Vdd (5V) and Vss (GND) with the wiper attached to Vo or Ve whichever nomenclature your LCD uses.
Adjust to half way, then powerup the LCD as I have indicated in my previous post and adjust until you see top row of black boxes as shown in the attached photo.