Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/c7a98e25604b87da860b83d2c47a4c2d.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563