Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/f38a42b76f2e1d77ab9a11573f4b740d.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563