Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/a5fc4ec3ac8125d21c7b7573b5d5d441.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563