Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/0ca8a627951eeba31414c1ced23cf4d0.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563