It's already been discussed, and it's related to the recent DDOS attacks on the server. It's been disabled for 12-24 hours whilst the transfer to cloudflare is taking place. Take a look around this section, before you ask a question that's already been asked.
Quote from admin from the other thread:
It helped against the DDoS somewhat. I'll bring it back up in 12-24 hours once the transition to Cloudflare is complete.