You need to upgrade your account from private to business. Private accounts are only for those selling off their old no-longer-wanted possessions from wardrobe and attic. Anyone who makes, grows, refurbishes, or buys in (new or old) items to sell, is a business and must be registered as such. Not only an Ebay requirement but the law. Go to Ebay's Seller Centre (foot of any page) for confirmation, and to the government's website for full information. And note that there is no such thing as a 'hobby seller' in this country, and how much or how little you sell or make is totally irrelevant.
You've been extremely fortunate not to have been caught by now, so best to upgrade as a matter of urgency, before you find yourself in deep doodoo - with Ebay for defrauding them of listing fees, and with Trading Standards for breaking consumer law and effectively denying your buyers their legal rights.
If you continue to have problems after you've upgraded, come back for further advice.
@honza-s
