Reply To: Featured Image Size in Blog / Comments off

[Tom]

You could try something like this:

add_filter( 'generate_page_header_default_size','tu_single_featured_image_size' );
function tu_single_featured_image_size()
{
    if ( is_single() )
        return 'medium';

    return 'full';
}

Adding PHP: https://generatepress.com/knowledgebase/adding-php-functions/

Have you checked the settings for the individual pages under “Quick Edit” to see if comments are turned on?