Curl /authorize endpoint gives 404

I’m new to Okta and I’m trying the token exchange flow but got stuck at the /authorize endpoint.

I curl the following endpoint and got 404.

curl -I "https://<okta test instance>.oktapreview.com/oauth2/default/v1/authorize?client_id=<my native app client id>&response_type=code&scope=openid&redirect_uri=com.oktapreview.<okta test instance>:/callback&state=teststate&code_challenge_method=S256&code_challenge=qjrzSW9gMiUgpUvqgEPE4_-8swvyCtfOVvg55o5S_es"

The error is:

location: /error/404?fromURI=...

Appreciate any help. Thanks!