Apparently the Jetpack alpha 13.8-a.1 that my Wordpress dot com site just updated to automatically, that I cannot work out how to roll back and is auto managed by WP, does not like the ActivityPub plugin! For the past hour or two my site was showing "Required class not found or not readable: Activitypub\Integration\Opengraph" instead of the actual blog. I switched off AP for now. /cc @pfefferle