Shortcode registered from a plugin not recognized

Your shortcode action is wrong/incomplete:

function ss_register_shortcodes() {
    add_shortcode( 'embed-slideshow', array( $this, 'ss_shortcode_embed_slideshow' ) );
}

Since you are doing OOP, you have to use the class method in object context (or static).

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)