You could try another browser or computer first, it could be your particular system. I managed to log in.
You could also try clearing your cache and switching to a different browser. You could try changing your DNS to Google's. (8.8.8.8 or 8.8.4.4). Also, check whether your firewall settings are blocking DZ!
@Markypie They posted about having trouble on their Facebook, guessing it was down for a while. Should be up now? If not, follow them on social channels to keep posted.
