If you've sold an item using an in-app Hermes shipping label and the status shows as being returned to sender, please contact Support here and provide us with your return shipping address so we can ensure your item gets shipped back to you asap.
What next?
Once your item's back, make sure you refund the buyer in full for the transaction. Once you've refunded the buyer, if the buyer paid using PayPal you can contact Support to get your Depop fee back. If your buyer paid through Depop Payments then this will automatically be refunded to you.