If you bought the Royal Mail postage on Ebay, you will have to lodge a claim with Packlink, Ebay's postage broker, as that is who you paid and who your contract is therefore with. (As far as I know, Ebay no longer uses Shutl - they replaced them with Packlink.)
No idea how you do that as I never buy my postage here, but the information will be in the Seller Centre, along with everything else you need to know about selling here. You also have the Help pages with their integral search to refer to.
@102vespa
@clute21
