Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/d805576c56c4ec5eabdb8f4f9d748518.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563