Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/8dba0df1e8b7f2e6f3c50fe634b13654.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563