How to request a refresh token with identityserver4 - asp.net

Question

I have IdentityServer and a separate WebApi project using resource owner flow.
When I request a token as below the token is issued and can be used to access the WebApi. So I assume IdentityServer is setup correctly, and the WebApi project is setup correctly as well.
username=user1
password=user1password
grant_type=password
client_id=myClientId
client_secret=myClientSecret
scope=api1
Now when I change the grant type to refresh and the scope to offline_access I get a refresh token. I then use the refresh token to get an access token, but when I use the access token to request the WebApi it is rejected.
With an error
the audience is invalid
I suspect it's because I am asking for an offline_access scope instead of api1 scope which the WebApi project expects. How do I get a refresh token that can use used with the scope api1?

Answer 1

var model = {
client_id: "myClientId",
client_secret: "myClientSecret",
scope: "api1 offline_access",
token_type: "Bearer", //Optional
grant_type: "refresh_token",
refresh_token: "your refresh token"
};
//this is most important step when to use refresh token
var base64 = btoa(model.client_id + ":" + model.client_secret);
//and your request here
this.$http({
method: "POST",
url: "/connect/token",
headers: {
'content-type': "application/x-www-form-urlencoded",
'Authorization': "Basic " + base64
},
data: jQuery.param(model)
})
.then(
response => {
//success
},
response => {
//logout
});