Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/78c2f9adb03db7bb2d3386e1d8a6b4e3.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563