A couple of posts that might help:
https://community.ebay.com/t5/RESTful-Sell-APIs-Fulfillment/c-eBay-Utility-going-round-in-circles-tr...
https://community.ebay.com/t5/RESTful-Sell-APIs-Fulfillment/the-provided-authorization-grant-code-is...
In addition, the response from shipscript on the other post shows the implementation in php.
Also, don't post any tokens, or credentials you've encoded to the forums, that is a security issue...
So like is mentioned in each of those posts, you do not want the client_credentials grant type you are using, that gives an application token, you want a user token.
The user token is a 2 step process
What you want is to generate a URL first.
Use that url to log in.
When you log in the URL will update to a string that contains a code= &
Grab that, make a body that uses the grant type of authorization_code with just:
"grant_type": "authorization_code"
"redirect_uri": YOUR_REDIRECT_URI_HERE
"code": THE_AUTHORIZATION_CODE_YOU_GOT_FROM_RETURNED_URL_PARAM
This will return the refresh token and the access token.
You can then use:
"grant_type": "refresh_token"
"refresh_token": THE_REFRESH_USER_TOKEN_YOU_GOT
"scope": "your scopes separated by spaces"
on that refresh token from that point forward.
A rough example of the 1st half:
static string appId = "";
static string certId = "";
static string redirectUri = "";
static string scopeListString = "https://api.ebay.com/oauth/api_scope https://api.ebay.com/oauth/api_scope/sell.inventory https://api.ebay.com/oauth/api_scope/sell.marketing https://api.ebay.com/oauth/api_scope/sell.account https://api.ebay.com/oauth/api_scope/sell.fulfillment";
static string oauthsignin = "https://auth.ebay.com/oauth2/authorize";
static string oauthendpoint = "https://api.ebay.com/identity/v1/oauth2/token";
static string Generate_Url()
{
Guid uuid4 = Guid.NewGuid();
NameValueCollection qs = HttpUtility.ParseQueryString("");
qs.Add("client_id", appId);
qs.Add("redirect_uri", redirectUri);
qs.Add("response_type", "code");
qs.Add("prompt", "login");
qs.Add("scope", scopeListString);
//include or not, this works either way, but it might not be useful or implemented incorrectly
//oauth2 standards documentation is lacking and vague on how to implement correctly
qs.Add("state", uuid4.ToString());
return oauthsignin + "?" + qs;
}
Console.WriteLine("\nEnter the following URL into a browser and log in, grab param between code= and & once logged in:\n");
Console.WriteLine(Generate_Url() + "\n");
Console.WriteLine("Enter in the code= param you copied from the returned URL");
string codeinput = Console.ReadLine();
string body = $"grant_type=authorization_code&redirect_uri={redirectUri}&code={codeinput}"
response = client.UploadString(oauthendpoint, body);
json = JObject.Parse(response);
Console.WriteLine("This is the token response:\n");
Console.WriteLine(json.ToString());
