Why did the PO refuse the item? Was this a label generated by the seller, and it was insufficient to cover the cost?
Then, you need to contact Customer Services, explain the issue, and ask them to reissue the correct postage label, and this will be charged to the seller's account, if this was a return for a damaged or item not as described transaction.
Contact CS with the link below, sometimes advisable to try at 8 a.m. when live agents come on duty, and then there's more chance of Dublin answering.
https://www.ebay.co.uk/help/eua?id=5190
@redgym13
