pingbacks / trackbacks not working?

My website https://www.derekbeck.com/1775 is no longer showing pingbacks within the site itself (let alone others I imagine). That is, I write a post, and link to an old post, and now the old post gets no pingback. I have confirmed it is not a plugin issue, as I’ve disabled all of my plugins and added a new link back to another post and still got nothing.

Is anyone else having this issue? Perhaps due to the latest WP update? (Is there a way to downgrade a version of WP to test?)