Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/ce6c0e49c453d7c1d19ece2c323c8f8c.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563