Hi @asdffffwsev , you need to specify the user journey you wish to use. Example here.
<RelyingParty>
<DefaultUserJourney ReferenceId="SignUpOrSignIn">
...
Have you set up a sign-up/sign-in flow? You can download the starter pack in the doc you linked and it will contain one if not. Please let me know and I can help you further.
Thank you,
James