SSO Troubleshooting: 400 Bad Request during service provider-initiated SSO

Error

When single sign-on (SSO) is initiated from Foundry, the user is redirected to the identity provider’s login page but encounters an error before authentication begins. For example:
“The request cannot be fulfilled because the message received does not meet the security requirements of the login service.”

This is just one example from a specific identity provider; your system may display a different error message—or no message at all.

Explanation and Resolution

See 404 Page Not Found Error during SP-initiated SSO. 404 errors often have the same root cause as 400 errors.