SimpleSAMLPHP cannot read the metadata in XML format. It needs to be converted. SimpleSAMLPHP provides a convert webpage to do this. The converter can be found in you deployment of SimpleSAMLPHP. It should be at a URL like this https://mysp.mycompany.com/simplesaml/admin/metadata-converter.php?

Past the Metadata into the text box and press the 'Parse' button.

After parsing the data, you should have text box for saml20-idp-remote. Copy the contents of that box and save it to the {SimpleSAMLPHP Directory}/metadata/saml20-idp-remote.php file.

If everything was done appropriately, the SAML integration between SimpleSAMLPHP and GridGuard should be compelete!