read more doesn’t display

I think if( has_excerpt()) return false that’s way its return full content remove condition and only use the_excerpt() then it will work.

I have another solution that i use 🙂

$content = get_the_content();
$short_content = implode(' ', array_slice(explode(' ', $content), 0, 10));
echo $short_content;

this function returns 10 words of post. after echoing content you can add button code like

<a href="https://wordpress.stackexchange.com/questions/81745/<?php the_permalink(); ?>" >read more ...</a>

now you cant’t use <!--more-->