Refresh token for embedded login using auth0-js

I am using auth0-js ( 9.19 ).
For login
username: email.toLowerCase(),
password: password,
}, (err, res) => {
if (err) return dispatch(authError(err.error_description));
I am getting refreshToken as null.
Scope used: scope: ‘openid email profile offline_access’,
on Auth0 side:
I have a Single Page Application configured with Refresh Token Rotation enabled.

How can I use refresh token?