OAM -->> getting "/oam/server/fed/sp/sso -->> SystemError. re-try your action."

Hi, we configured federation services in OAM 12.C, we are getting successfully some 4 attributes on testspsso page But we are getting SSO Result as —» SSO Authentication Result

Authentication Failed with SSO Status Message No user returned during attribute based authentication using attribute mapping for name ID: <email> and name ID format = urn:oasis:names:tc:SAML:1.1:nameid-format:unspecified

We are getting when we run Okta as IdP url with error in OAM -->> getting "/oam/server/fed/sp/sso -->> SystemError. re-try your action."

Any Help would be appriciable.

Thank you.