A seller cannot close an account themselves if they have made recent sales, but eBay can remove that seller's account if they have broken some selling regulation.
Is the purchase still within 30 days of the item's last estimated date for delivery, and is missing a part which was described in the eBay listing? Then, contact eBay Customer Services , explain the situation and they can open that case for item not as described for you, for your refund.
This is the easiest and quickest way to contact eBay Customer Services, for a Call Back option.
https://www.ebay.co.uk/help/eua?id=5275&mkevt=1&mkpid
Lines open between 8 a.m. to 10 p.m. on weekdays.
9 a.m. to 6 p.m. on weekends.
I recommend contacting CS very first thing in the morning, when the lines first open, as there's more chance of Dublin answering.
@kokokat42