1) Always get the results from 'Test Connection.'
The error says: “Could not validate xml digital signature. Please confirm that the certificate that you are signing the SAML 2.0 response data with is the same certificate that you provided AtTask in your SSO SAML 2.0 setup.”
The Certificate is signed using DSA when Workfront is expecting an RSA signature.
FIX: Recreate the certificate and use an RSA signature instead of DSA.
XML data is not correct.
FIX: Re-export/re-import the XML metadata from ADFS.
The request could not be performed due to an error on the part of the SAML responder or SAML authority.
FIX: A problem on the SAML responder or SAML authority side of things.