Hi,
it seems to me that someoften the missing contrast makes all content of the lcd invisible. So be sure that you are using
-the correct pin for contrast ( I see often pin3, but also 4)
-the correct polarisation at contrast pin (some lcd want positve, some negative). Best thing to find it out by datasheet and avoid wrong polarisation.
-the correct voltage. I see everything from +5V to -15V. if you cant find any datasheet, you may try, but I dont know if one can kill his lcd by wrong polarity or voltage. So when trying, use ever a 10k or 20k resistor in serie to limit the current. I use a voltage regulator with adjustable current, so I can the voltage make very 'weak' by setting to a max. of about 10 or 20 mA.
As long as you cant see anything and cant set the contrast from dark to light, you cant be sure if the lcd is showing anything, so try to clear this point first.
Another thing are the many connection variants I see. So be sure that you use the right one for the lib.