Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/daa0e0633e005b98f2a3b0de96c3f942.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563