Bar Code on Priority mail shipping label not supported at the post office

We ship a few packages with USPS, we print the priority shipping label with shiprush without postage. We bring the package to the post office and they tell us that the they cannot scan the bar code on the label and they must place a new bar code that they generate over the bar code printed on the label. The problem being is that we now have absolutely no way of tracking these packages. The bar code saved in our system was auto generated by shiprush at the time the label was created. I am using V 10.2.7 for USPS.

thanks

Jeffrey Bart
Granite State Candy Shoppe