@cluong Hmm, Just to verify, when you submit the data, do you get a URL that looks similar to this?
https://sptest.iamshowcase.com/ixs?idp=581409a977a79eb0f979f2f591204c8f69f0f334
It does not surprise me that the WebAuthN Wizard would fail if we cannot get the url provided to work.
For clarification, it is my understanding that iamshowcase is the SP in this test case and FusionAuth is the IDP. I never used the "Initiate login URL" when setting up the SP initiated SSO.
For the record, if I enable "Enable IdP initiated login" from the SAML tab of the Application, I too am able to see the federated page.
When setting up the SP initiated SSO, I do not use the url provided by "Initiate login URL."
Would you be able to share the Metadata URL or the xml that it produces? Could you also share a copy of your Application -> SAML tab configuration. (feel free to mark it up and hide any information you do not want public.) If that does not work for you, I suggest setting up a test instance so you can share some more detail so we can get this working for you. Also, what version of FusionAuth are you working with?