If you are having any issues with labels printing out and looking distorted/missing information, I recommend you go into your Printing Preferences for the assosciated printer and make sure the below settings are set.
You can adjust the speed and darkness if you need too but bear in mind it may affect the quality of the barcode and render it invalid.
Once you've ensured your settings line up with the above, hit the apply button.
If you have gone through this article and are still having issues, please contact support who will be happy to help.