This happened since yesterday, I went to my favourite twinsword public server.
Then apparently, I see a message on the screen saying: "Not Connected"
I try to reconnect again and again but it keeps doing the same thing, I tried another server but it did the same thing like before.
I use the latest 2016 version of Toribash and I use OS X Yosemite (MacBook Air)
I hope this problem will be solved in the near future.

perhaps your password got reset and you need to login again
in the game.

Thanks, but I don't remember anything of me resetting my password but, when I logged in again with the same account and went into a server the not connected showed up again...

Can you join private servers?
Could you please make another account and try joining that same twinsword server and tell us what happens?

Okay, I tried another account, oh and I was back to normal again.
BUT I am still testing it out on my other wifi.

What about the private servers as Lite mentioned, are you able to join those?

maybe go in game and go to the login and click "Show" password to see if its correct and such, I don't know why its not working but I hope you can fix the issue soon bro

It looks to me that you were playing in a limited belt server(server's which name starts with Beginner, Intermediate, etc). Once you get above their belt limits you can't join them anymore and you'll need to move on to a next level server (ex: if you were playing on beginner and got blocked from it, you would have to start playing on intermediate and so on).