Unable to authenticate through REST API when using scratch org

Question

I'm having some trouble getting the REST API to work on a scratch org. When I call the login endpoint I get the error "invalid grant". (This happens when I try test.salesforce.com as well as login.salesforce.com.) My code works fine with logins for non-scratch orgs; it's only my scratch org that causes this error.

Here are the steps I've followed:

1. Create scratch org with sfdx commands.

2. Open scratch org and set a password for the user.

3. Reset security token.

4. Create a connected app, and copy the consumer key and consumer secret.

5. Edit the connected app policy and relax IP restrictions.

When I perform these steps and put all the required values in my request, it works fine if I'm using a non-scratch org, but I get an "invalid grant" error for a scratch org.

What steps am I missing? What is it about scratch orgs that makes this not work?

EDIT: Here is the relevant C# code:

public SalesforceClient Login()
        {
            SalesforceClient sfClient = new SalesforceClient();
            String jsonResponse;
            using (HttpClient client = new HttpClient())
            {
                HttpContent request = new FormUrlEncodedContent(new Dictionary<string, string>
                    {
                        {"grant_type", "password"},
                        {"client_id", sfClient.ClientId},
                        {"client_secret", sfClient.ClientSecret},
                        {"username", sfClient.Username},
                        {"password", sfClient.Password + sfClient.Token}
                    }
                );
                request.Headers.Add("X-PrettyPrint", "1");
                HttpResponseMessage response = client.PostAsync(sfClient.LOGIN_ENDPOINT, request).Result;
                jsonResponse = response.Content.ReadAsStringAsync().Result;

Answer 1

I figured it out. All I had to do was remove the token from the password field. The token is not required at all. I have no idea why this is the case, so if anyone has an explanation, please let me know!