The shipping label isn't being accepted because incorrect dimensions and/or weight were assigned to the package. In the case that an entirely new label is required, you may purchase a new tracking number and add the tracking number to your swap page. SidelineSwap can reimburse you up to the amount paid for by the Buyer, minus non-refundable processing fees.
Once you have your new tracking number, you can add the tracking number directly to your swap page by clicking "Update Label", "Use My Own Label", and then adding the tracking number with the correct carrier.
If there is a slight difference in the DIM weight of the label and the DIM weight of the package, please contact Support. We can provide you a new label. You also may have the option of paying for the difference in postage out of pocket. In the interest of getting the package shipped ASAP, this is encouraged.