What could be the problem? The compatibility with LiquidCrystal Library? I should use LCD 4-bit library? Or another thing?
We really need to know more about the specific device you have. Is it really a 'shield' that plugs directly into your Arduino or is it a separate pc board that has to be connected with jumpers?
I think that is a 'Powertip' part number and as I recall some of them are use a non-standard pinout.
The LiquidCrystal library should work if you connect things correctly and set up the parameters correctly.
The LCD 4-bit library should be deleted from your computer so that you don't use it by mistake. It is a poorly written library (read the comments if you want proof) that was cobbled together before the standard LiquidCrystal library was updated several years ago.