NOTE: Please ignore.
Imported entries are not showing the trackback URL link. I have found the trackback:ping URL in the source of a post (Indexablog) to which I will try and send a trackback. Not a good long-term solution.
For future, more complete troubleshooting see also: Template TagsTrackback URL.
Immediate Update: Did not seem to work; but then WP is having issues again tonight; i.e. whenver I save something the action works but the page goes completely white/blank.