You need to refer to the email with details of the guarantee that you were sent when you bought the item.
This is between you and the seller so you need to contact the seller by email phone or letter. The Ebay Money Back Guarantee covers you for 30 days, even for a certified reburbished item.
If you don't get anywhere with the seller, you can try your payment provider but they only offer help for a limited period.
Details here:
https://pages.ebay.co.uk/refurbished-guarantees/
Your seller guarantee information
All Refurbished items come with a minimum 12-month seller guarantee (available on orders sent to a Mainland UK delivery address). The guarantee covers any defects in functionality.
Once your order has been confirmed, the seller will send you a separate email with details of the seller guarantee, what's covered and their contact information. Alternatively, this information will be included in the parcel when the item is sent to you.
Please make sure you hold on to this information for the duration of the guarantee.
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)
