As told by an Airport Operations Crewmember:
A woman came up to me in the airport all upset. She told me that she had tried repeatedly to print out her boarding pass from home, but she apparently was doing something wrong. She then showed me a stack of boarding passes, successfully printed out. I asked her what was wrong as it looked like she had printed them out just fine. She said that the long sticker that you put on your suitcase wouldn’t print out for her!