What you were expecting to happen, and what actually happened?
Play a ranked pvp game
What are the steps to make it happen again?
Do you have any screenshots or video you want to share with us so we can see the problem? Attach them to your post!
This error has occurred for me both on Steam and on Mobile (oddly enough while I was having steam confirm the integrity of its cache. A window pops up and directs me to the support site and forces a restart.