Looks like your server does not support wp_remote_get() function which is a default WP function btw. wp_remote_get() uses loopbacks and this could be the reason why you are unable to import complete pre-made layout. So or you will contact with your admin and ask him if he can remove those limits for you or you need to import demo without paying attention to errors and after that import muffin options manually.
Comments
Looks like your server does not support wp_remote_get() function which is a default WP function btw. wp_remote_get() uses loopbacks and this could be the reason why you are unable to import complete pre-made layout. So or you will contact with your admin and ask him if he can remove those limits for you or you need to import demo without paying attention to errors and after that import muffin options manually.
More details about similar issue you can read on http://forum.muffingroup.com/betheme/discussion/12103/wp-remote-get-demo-download-no-header-menu-of-footer-settings where a problem was a little bit different but the solution may work for you as well.
Thanks!