Feed is not vaild

Hi there!

Im using the FeedBurner Plugin to serve my WordPress rss feed.
The W3C Feed Validation Service tells me that my WordPress rss feed is not valid: https://validator.w3.org/feed/check.cgi?url=http%3A%2F%2Ffeeds.feedburner.com%2FAbusech

The strange thing is, that when I look at my rss feed https://feeds.feedburner.com/Abusech it is blank :/ But when I take a look at the source code of https://feeds.feedburner.com/Abusech I can see some content :/

Can somebody help me?