Pingback / Trackback issue

I’m making a list of updated posts for the blog category of my site and I want it to pingback/trackback the posts that have been updated. What’s weird is that some of the posts linked in it automatically were hit with the trackback comment, some I had to past the trackback in and then it worked, and then the rest (about 17 of 20, something like that) don’t show up with any trackback.

How can I troubleshoot this? I’m not sure where to look to find out what’s happening.

The trackback links show up under the “Already pinged:” section when I edit the post, so it seems to be keeping tabs on that.