I don't know what exactly is going on but I had something similar to this in Matsuri today, waited for 5 minutes first thinking my opponent was lagging, this ended up not being the case as after those 5 minutes a message popped up saying something like internal issues please be patient and don't leave the game. (don't know exactly what it said as I forgot to make screenshots, * me) So I waited for about 15 minutes, but nothing happened... In the end it took me too long and I did refresh which of course counted as a loss which was highly annoying because the opponent was weak and probably long gone before me, and I could've won easily, now I lost rewards as I only had 1 win (which has happened multiple times already during Matsuri).
For some reason if something happens it is always in Arena or Matsuri so I seriously started disliking cross server events, would be nice if they actually get fixed one day.