Hi EJV, It looks like arena's is down right now. You can try connecting with the direct connect, which is 142.4217.143. Or you can log in and see if a moderator can tp you out.
It happened because you logged off in Hide and Seek, and then either Hide and Seek or Arenas crashed. When you connect to Sandlot, it always tries to connect you to the server you were on last, and if that server is crashed, you won't be able to login at all. This is why I always recommend that you return to the lobby before logging out.
It will help you once, and then a direct connection will also save where you logged out, so if you use the IP and logout in Hide and Seek and it crashes, the same thing will happen again.
