Are you still within 30 days of the item's last estimated date for delivery.

Then, contact Customer Services,  explain you are trying to return a faulty item but the seller has provided an invalid return label, ask CS to send you the correct label,  they should,  and they'll charge  it to the seller's account.

Contact CS with the link below for a Call Back option.,  Try at 8 a.m. on weekdays as there's more chance of Dublin answering.

https://www.ebay.co.uk/help/eua?id=5190

@kanekane96