That’s because Twitter Feed is down! TwitterFeed.com feeds around 170k feeds into Twitter (that’s a lot), and I’m not sure what type of system they are using for this, but it is very unstable – in my opinion.
Even when TwitterFeed.com is up, the site is EXTREMELY slow at processes requests. What I mean is, when you click on link within your profile, it can take several minutes to actually load.
I myself am a heavy user of TwitterFeed.com, and I have multiple Twitter profiles for affiliate products. As of right now, they are the best option of sending content via RSS feeds into Twitter.