Can't connect to certain games

every 1 in like 20 games there's a game where the game WILL NOT let me connect no matter what and i can't do anything until the game ends, it just goes to a black screen and then a popup says Unable to connect to the server please check your network connection and try again, whats up with that? why is it only once in a blue moon and not every game? its pretty annoying just not being able to play a game i started and having to wait for no reason