Setting Up Phoenix with Okta OIDC: Redirect URI Issue Explained

I'm trying to setup phoenix with okta OIDC following instruction at https://docs.arize.com/phoenix/self-hosting/authentication#other-identity-providers. I have had all three env vars set up

PHOENIX_OAUTH2_OKTA_CLIENT_ID
PHOENIX_OAUTH2_OKTA_CLIENT_SECRET
PHOENIX_OAUTH2_OKTA_OIDC_CONFIG_URL

but on login page, I'm seeing error related to Your request resulted in an error. The 'redirect_uri' parameter must be a Login redirect URI in the client app settings:, some more description is available at https://support.okta.com/help/s/article/The-redirect-uri-parameter-must-be-an-absolute-URI?language=en_US, looks I'm missing a redirect_uri , does anyone know what it could be in the context of phoenix+okta ?