IdentityServer3 Response status code does not indicate success: 400 (Bad Request) - asp.net-mvc

Question

I always get Bad Request 400 from IdentityServer3. I am trying for 3 days now but no luck :( Anyone could please tell me what am I doing wrong?
I am trying to access IdentityServer3 hosted by another vendor that I have no control. The vendor has asked us to implement Implement OAuth2 authentication with Bearer token. The vendor provided us with the Client ID, Client Secret and the URL to be used is http://www.xxxxxx.com/identity/connect/token
The vendor told us to use to request bearer token and use it in the request headers Authorization: Bearer
I can successfully obtain the bearer token from vendor. But when I call the
GET /api/profiles/myemailaddress#gmail.com I get Bad Request 400
Here is what I have done:
TokenClient client = new TokenClient("http://www.xxxxxx.com/identity/connect/token", "myclientid", "myclientsecret", AuthenticationStyle.PostValues);
var response = await client.RequestResourceOwnerPasswordAsync("myemailaddress#gmail.com", "mypassword", "profile"); // successfully gives me the token
i got the access token, now i want to use the token to request user profile:
var clienthttp = new HttpClient();
clienthttp.BaseAddress = new Uri("http://www.xxxxxx.com");
clienthttp.SetBearerToken(response.AccessToken);
var json = await clienthttp.GetStringAsync("http://www.xxxxxx.com/api/profiles/myemailaddress#gmail.com"); // error Bad Request 400
Additional Info:
"scopes_supported":["profile","offline_access"],
"claims_supported":[]
Thank you.

Answer 1

The vendor was expecting additional value in the header. Since my request was missing that additional value, they returned Bad Request. I had to modify my code to find the exact reason of bad request.
Here is the updated code, might be useful for someone:
var client = new HttpClient();
client.BaseAddress = new Uri("http://www.xxxxx.com");
client.SetBearerToken(response.AccessToken);
var callApiResponse = client.GetAsync("api/profiles/myemailaddress#gmail.com").Result;
string tokenresponse = callApiResponse.StatusCode.ToString();
string clientresult = callApiResponse.Content.ReadAsStringAsync().Result;
tokenresponse: "Bad Request 400"
clientresult: "Missing CompanyID in the header"
Then I knew that they also expect companyid in the header so I added it. then all was good.
client.DefaultRequestHeaders.Add("CompID", "xxxxxx");

Answer 2

I had a similar error (Response status code does not indicate success: 400 (Bad Request)) for different resource not identity server. i manage to resolve that using FormUrlEncodedContent
Refer below code
using (HttpClient client = new HttpClient())
{
string baseUrl = "https://*******.com/****"
Dictionary<string, string> jsonValues = new Dictionary<string, string>();
jsonValues.Add("username", "******");
jsonValues.Add("password", "******");
var contenta = new FormUrlEncodedContent(jsonValues);
var response = await client.PostAsync(baseUrl, contenta);
using (HttpContent content = response.Content)
{
string data = await content.ReadAsStringAsync();
if (data != null)
{
Console.WriteLine(data);
}
}
}