i got Blank Labels from the printer ?!

hi

how are you guys ..

i hope you all fine

here

i have PRINTER from zebra Company for labels, Model (GK420T), and i'm using windows form VS 2012/C# , and i want to make reports from Crystal Reports

so i tried  first to print it from Crystal report viewer window and it's working very well , but when i tried to print the labels directly From

PrintToPrint(..) Method  i got blank label from printer !!

so .. what's the problem ?! and how can i fix it ?!

thank you a lot guys .