Ids4 + Okta Integration

Hello, I´m currently trying to integrate Okta and Ids4 and after reading the documentation at Add an external Identity Provider | Okta Developer I´m still having some problems.

Firstly I´m not sure about how can someone login in Okta without using Okta credentials.
Secondly if I have correctly understood the doc up there in this message, the flow is as follows:

  • Login in Ids4
  • With the info the response returns, build a URL with this structure:

&state={state (recovered from Ids4 login response)}
&nonce={nonce(recovered from Ids4 login response and decoded)}

  • Get redirected to my app.

Currently this last step is not working, and all I get, no matter what I change in that URL, is a 400 Bad Request Error page.

Is there something I am missing or that I could,ve misunderstood?

Thank you for your time.