Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/10cf8a6dfc20d29cfbd35ee3a1887247.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563