Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/bd7c1d2605d3bde8f66c1692cf7b06c1.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563