Preview returns 404 in theme [closed]

Question

I have a theme which appears to have broken previewing posts. When I preview a page/post I get a 404 error.

If I change to another theme previews work fine again so it must be something in this theme.

I can't work out when/if I would have broken previews. Going through my filters and actions I can't see anything obvious.

Has anyone had a similar problem/ What did it turn out to be?

Answer 1

This is just a shot in the dark without knowing more like sMyles said. Try saving (flushing) your permalinks. If you have recently changed the structure of your URLs, simply by going to Settings > Permalinks and click Save Changes might resolve this issue.

Answer 2

I found the answer.

It was only for post-formats on pages. The issue was that I needed to also register the taxonomy post_format on pages as well in the init action.

I have updated the wiki page to reflect this. https://codex.wordpress.org/Post_Formats#Adding_Post_Type_Support

// add post-formats to post_type 'page'
add_action('init', 'my_theme_slug_add_post_formats_to_page', 11);

function my_theme_slug_add_post_formats_to_page(){
    add_post_type_support( 'page', 'post-formats' );
    register_taxonomy_for_object_type( 'post_format', 'page' );
}