IDP entity ID not found in SP

Exception (on SP, with Artifact Binding): 

SAML2

Exception:

Couldn't find IDP based on the SourceID in the artifact.

com.sun.identity.saml2.common.SAML2Exception: Couldn't find IDP based on the SourceID in the artifact.
 at SPACSUtils.getIDPEntityID(SPACSUtils.java:432) ~[opensso-openfedlib-2.5.1.jar:?]
 at SPACSUtils.getResponseFromArtifact(SPACSUtils.java:283)

Reason:

The SP does not find the IDP's entityID in its configuration.

This is either due to:

1. The IDP's entity id does not match the local configuration, please check both XML files of the IDP and the SP's configuration in IAM to verify that all places use the same entity id.