"Caused by: org.opensaml.ws.security.SecurityPolicyException: Validation of protocol message signature failed"
is a SAML signature verification error.
It seems like one of the sides of the SAML partnership does not have the correct keys or certificate, or otherwise is misconfigured.
IDP digitally signs the payload (SAML Assertion) with its key, the Console verifies the signature using the certificate.
The cert needs to match the key.
If the receiver (AIP Console) has the wrong cert, or a cert that does not correspond to the signing key, then you can get this kind of signature validation error message.
So, check your keys.