Featured images not showing up

Question

I´m having a strange issue with featured images. Here´s what I did:

1. Added theme support for featured images with add_theme_support( 'post-thumbnails' );
2. Attached a featured image to each post
3. Included the template tag inside the loop: the_post_thumbnail();

Strangely the featured image isn´t showing.

However, when I create my own img element it does show up:

<img src="' . wp_get_attachment_url( get_post_thumbnail_id($post->ID)) . '" /> 

Does anyone have an idea of what could be the issue here? Or where I could start to look for a solution?

I´m not even sure where to start troubleshooting, so all suggestions are welcome!

Answer 1

Finally found the issue: I was using a filter in my site specific plugin to remove image attributes. Somehow it also deleted the full image URL.

add_filter( 'post_thumbnail_html', 'remove_img_attributes', 10 );

Removing that filter solved the issue.