Hi lennart,
Thank you for reaching out to us. I tested the following code and it works fine:
// Excerpt More String
// =============================================================================
if ( ! function_exists( 'x_excerpt_string' ) ) :
function x_excerpt_string( $more ) {
$stack = x_get_stack();
if ( $stack == 'integrity' ) {
return ' ... <div><a href="' . get_permalink() . '" class="more-link">' . __( 'Read More', '__x__' ) . '</a></div>';
} else if ( $stack == 'renew' ) {
return ' ... <a href="' . get_permalink() . '" class="more-link">' . __( 'Read More', '__x__' ) . '</a>';
} else if ( $stack == 'icon' ) {
return ' ...';
} else if ( $stack == 'ethos' ) {
return ' ... <a href="' . get_permalink() . '" class="more-link">' . __( 'Read More', '__x__' ) . '</a>';
}
}
add_filter( 'excerpt_more', 'x_excerpt_string' );
endif;
Make sure you’re adding it in the child theme’s functions.php file. Also make sure the EXCERPT LENGTH is set correctly under Theme Options > Blog > Content (see screenshot)

You can adjust the value as per your need. When i test it in my local setup i see the Read More button (see screenshot)

Hope this helps!