Refresh token when using Okta.AspNet middleware in MVC application

I am using Okta.AspNet middleware in a MVC applicaiton and using default org authorization server for authentication. Everything works as expected but my user claims doesn’t have a refresh token even though I have refresh token option checked for my app under allowed grant types.

I am getting back id_token and access_token but no refresh token. Is this expected behavior? Am i missing something?