Flush Rewrite Rules · Issue #2 · indieweb/wordpress-mf2-feed (GitHub) When I activated the plugin, I had to manually flush the rewrite rules to get it to work. I installed and activated the plugin from my WP Dashboard. After, I found my /feed/mf2/ urls are 404s. I flushed the rewrite rules (Dashboard -> Settings -> Permalinks -> Save Changes). Works now.