Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/8dd2d8d9de8e5d450846e49cb00c56f9.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563