Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/bd7d8cd9fec0275a39fe4f31f1ab97d1.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563