This is most likely a configuration problem on either the service provider or identity provider.
The debug information below may be of interest to the administrator / help desk:
SimpleSAML\Error\MetadataNotFound: METADATANOTFOUND('%ENTITYID%' => '\'http://users.consno.it\'')
Backtrace: 3 lib/SimpleSAML/Metadata/MetaDataStorageHandler.php:343 (SimpleSAML\Metadata\MetaDataStorageHandler::getMetaData) 2 lib/SimpleSAML/Metadata/MetaDataStorageHandler.php:363 (SimpleSAML\Metadata\MetaDataStorageHandler::getMetaDataConfig) 1 modules/saml/lib/IdP/SAML2.php:381 (SimpleSAML\Module\saml\IdP\SAML2::receiveAuthnRequest) 0 /var/www/vhosts/consno.it/auth.consno.it/saml2/idp/SSOService.php:19 (N/A)
This error probably is due to some unexpected behaviour or to misconfiguration of SimpleSAMLphp. Contact the administrator of this login service, and send them the error message above.