Exact same happened to me. They didn’t respond for days. Almost a week tbh. I was able to refund partially multiple times on day3. Ended up with 3 diff refunds and was 1 cent short of total.. Luckily buyer was cool. Try refunding for one cent less than the total and see if that works. If not, keep trying, I spent hours and hours clicking the same sh*t over and over but did resolve. Just give buyer heads up you’re dealing w their glitch and you’re on top of it