I see we're already working with you on this via email, so we'll just continue the discussion there. Here was our reply in case anyone else with a similar issue happens across this thread:
As far as we're aware there is still an ongoing nightly embargo on orders placed through eBay which lasts from 5-8am GMT, which should be approx. 7-10am for your time zone (GMT+2).
We'd first recommend you check to see if the order has since been listed in your Dashboard under View Order History>Transaction Log, which would confirm whether or not we did process the sale. If so, you might ask the buyer to check their Spam folder and mark the message as Not Spam if they find it there.
Otherwise, this Help page covers the most common reasons eBay orders are having trouble processing:
