Chris, I've disabled Pingbacks on my WordPress due to an extensive and annoying amount of spam.

However, I did send a webmention at 2016-03-10 16:01:01, which I've checked now. The response was:

error: no_link_found
error_text: The source URI does not contain a link to the target URI.
code: 400
message: Bad Request

This is a problem. The source was, the target was and that URL on my site does contain an href attribute with this exact URL to your site.

Any idea what could have gone wrong?