Alt tags working on blogs, but not on thumbnails on main blog page

Hello there!

If you use the following code to display featured image on your main blog page:

<?php if ( has_post_thumbnail() ) : ?>
    <a href="<?php the_permalink(); ?>" title="<?php the_title_attribute(); ?>">
        <?php the_post_thumbnail(); ?>
    </a>
<?php endif; ?>

The ALT text you’ve entered for your featured images should appear. Make sure the ALT text is entered properly when you assign the featured image to the post. (It should look like this.)

If this doesn’t fix your problem, please provide a Gist or Pastebin of your theme template file, and we can investigate further for you.

Cheers!