Are you still unable to access the ddnet.tw and status.tw websites? Because that can impossibly be caused by a problem with the masters and therefore must be an issue somewhere at your side. Maybe even at the side of your provider, who knows.
When you cannot connect to a teeworlds server by IP but your friend can, than that is also not a problem with the masters. Their task is just to inform you about all the teeworlds servers that exist (only their IPs!); but sending you the serverinfo and letting you connect is entirely the task of the gameservers themselves.
Maybe you installed or updates something or something updated itself without you even noticing it and causes these issues now.... Or it's really just your provider having some trouble with whatever... There are so many possibilities what may go wrong. The only thing that I'm pretty sure about is that it's not a teeworlds-sided thing, from what you told.