Auth0 pkce flow

I have been working on pkce flow where I am making a call using msteams sdk for /authorize endpoint and I am able to get code successfully but when I try to make a fetch call for access token at /oauth/token endpoint it is giving me an error of cors. I am using ngrok for tunneling and I have added my ngrok URL in auth0 registered application settings but I don’t it is still giving me a cors error for that.