Unable to Complete Transaction

I've never seen this red dot and text that says "we were unable to Complete this translation". This item has been delivered over three days, and I saw this to see why I hadn't been paid out yet. Anyway, I took the support "get help" path to see what Mercari says. I actually had messaged the buyer a couple of times and got no reply, so I didn't bother messaging them again. Has anyone else seen this message before though?