Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/27e7e9cf6de2a3e24c40ba215cb2b5c6.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563