No printing

Hi,
I have a Zebra S-500, when i try to print the label the label comes out blank (white), i understand why, i don't receive any error message, the ribbon is good and also the blank label is compatible, before i don't had this problem with this label and ribbon, also the sensor see's the label because it is automatically stop at the end of the label, please someone can help me to resolve this problem.

Best regard