Trackback links result in error

Hi All;

New to the blog world. I notice that the trackback links in my messages are resulting in an error.

See https://www.writingwhitepapers.com/blog/2006/07/11/how-much-do-you-charge-to-write-a-white-paper/ for an example.

I get an error 302 Found. Any clue what is going on?

Mike