According to a video on YouTube here
you can validate via your Twitter account - Twitterfeed
As to try and help you I've gone ahead and created a twitterfeed account and I've managed to
validate without any trouble http://prntscr.com/8g1czc
however when I entered my standard URL www.midnightgaming.uk without adding the "/news/rss" it would not validate, as you can see http://prntscr.com/8g1duw
Moving on, so I've followed the 3 simple steps and created a active service...and guess what it works!!! http://prntscr.com/8g1mzl
I surprise myself sometimes.
Right, so yeah..sorry pretty chuffed that I managed to get this working seen as i'm a newbie to RSS ROFL! Looks like you entered the wrong URL...I think*