When you challenge someone on OGS as a friend, it should be made more visible to the challenged. I’ve tried challenging a few people on OGS but they seem to not notice it. It could be that they are afk, but I think it could also be due to the fact that challenges are only visible if you click the notifications tab in the top right. It would be nice if a pop-up alert would show up on the screen to let you know that you’ve been challenged. A good example would be on Fox or Tygem (I believe).