If you display a Twitter feed in a widget or Page or Post on your WordPress Website you may be getting errors displaying the Tweets. Errors range from just not showing Tweets to Error fetching Twitter RSS feed, This does not appear to be a valid RSS or Atom feed, A feed could not be found at http://api.twitter.com/ … and so on.
Twitter has recently changed the way that it distributes feeds and it’s a bit more complex to setup. Actions within the Twitter account are necessary in order to be able to show Tweets in a feed on a Website.
The best thing to do to resolve the problem is update the Plugin or Theme that provides the Twitter Feed widget or functionality and follow any new instructions on how to set up the feed. If your Theme or Plugin hasn’t yet been updated to cater for the new Twitter requirements then search for a Plugin that does provide the new functionality.