eBay are blocking your messages as the refund falls outside their 30 day MBG and they do not get involved in guarantees outside that period.
However, it sounds like you purchased this from a UK business? If so, find the item in your Purchase History. On that page go far right to See Orders from. Select the date of purchase find the item, scroll down the listing you should have the business seller's address and contact details.
@allisoncarl