Facebook's NetworkedBlogs States My Feed URL is Wrong

My blog is syndicated with NetworkedBlogs and was working fine but it’s now stopped picking up my latest postings and only shows my old posts. When I check it out I get told that my feed URL is wrong or there is a problem in the feed itself. NetworkedBlogs insist the problem is not with them but with my feed from my blog.

Can I be guided in how to correct this problem?