It's likely the server that you're connecting to either having problems or being overloaded, or possibly something in your network, their network or all the networks in between causing issues connecting to that specific server (for example, maybe it uses a port that your ISP blocks). I'd suggest googling things to see if other people are having the same problems (the game's Twitter account would be a good place to start looking, too), but sometimes these things just happen - too many people trying to connect can have the same effect as a DDOS attack because servers can only serve so many clients, so if there's been a recent update or something it can be hard to connect. It should pass, though.