IDP does not find RP Metadata

[Rainer Hoerbe]

An AuthnRequest from a specific SP leads to a 'metadata not found‘ message, while other SPs work.

INFO [org.opensaml.saml.common.binding.impl.SAMLMetadataLookupHandler:128] - Message Handler:  No metadata returned for https://shib.lms-staging.km.co.at/shibboleth in role {urn:oasis:names:tc:SAML:2.0:metadata}SPSSODescriptor with protocol urn:oasis:names:tc:SAML:2.0:protocol

The metadata provider in metadata-providers.xml is "/opt/md_feed/metadata.xml“. When I grep it for the EntityID the ED is found:

$ grep https://shib.lms-staging.km.co.at /opt/md_feed/metadata.xml 
<md:EntityDescriptor entityID="https://shib-lms-staging.km.co.at/shibboleth">

And it does have a role:

<md:SPSSODescriptor AuthnRequestsSigned="1" protocolSupportEnumeration="urn:oasis:names:tc:SAML:2.0:protocol urn:oasis:names:tc:SAML:1.1:protocol urn:oasis:names:tc:SAML:1.0:protocol">

The metadata is fresh and there were no warnings from the MetadataResolver. How can I trace this problem? I set idp.loglevel.opensaml=DEBUG, but I do not see what is going on.

 - Rainer