The most common cause is placing tape over the shipping label. Do not place tape or any other material over your shipping label. 

One of the benefits of Rollo is that shipping labels already have adhesive. You simply need to peel and place the shipping label on your box. 

Please do not place any additional tape on top of the label. The adhesive chemical in the tape can react with the shipping label and cause it to fade. Furthermore, tape can add reflection to the content of the label which will make it more difficult for scanning.