You cannot report this to eBay as they do not offer warranties or guarantees on items, just that they are just as described on receipt. If they are not, a buyer has 30 days under eBay's 30 day MBG, Money Back Guarantee policy, to return the item for a full refund.
Postage would be covered by the seller if within that 30 day period. If you pay for this now and send it back you have no protection from eBay that the item will be fixed or replaced, your trust would now be solely with the seller.
If purchased from a registered UK business, who offered a guarantee and is now not upholding this, then turn to Citizens Advice for your next steps, if you wish to take this further.
@shiraz786shiraz
