using restsharp for oauth2 in vb.net - vb.net

Question

I'm new to oauth2, but I have tried my best to learn it.
this should be just a simple first step into getting token.
so the situation is like this.
I have succeeded trying it with postman web, but postman desktop always failed (callback timeout or Esockettimeout).
what I did was only filling in the type oauth2, granttype = client_credentials, client id = client_id and client secret = client_secret.
I dont know why, I have tried to view the console and making sure all parameter is the same. I have tried to disable my firewall and antivirus, and disable proxy and ssl on postman desktop's setting but still the same.
so I tried with powershell and iwr. using this :
iwr 'https://thesite.com/token?grant_type=client_credentials' -Headers #{ 'Authorization' = 'Basic OAuthE='} -Method "POST"
of course "thesite.com" should be my site, and "OAuthE=" was the authorization base64 from clientid:clientsecret.
this was successful in getting token.
I did it just to prove that my router and firewall setup is ok that the request and the token should be able to pass through.
so I tried to translate this to .net with newest restsharp (108.0.3).
Dim client As RestClient
client = New RestClient("https://thesite.com/token")
client.Authenticator = New HttpBasicAuthenticator("clientid", "clientsecret")
Dim Request = New RestRequest(Method.POST)
Request.AddHeader("content-type", "application/x-www-form-urlencoded")
Request.AddParameter("grant_type", "client_credentials")
Dim response = client.Execute(Request)
MsgBox(response.Content)
with this, response.content always empty, and response.statuscode always 0.
I have tried many other ways like putting the client id and client secret in request.addheader or request.addparameter. I even tried the executeasync, like :
client.ExecuteAsync(Request, Sub(response)
Console.Write(response.Content)
End Sub)
but I'm not familiar with async, and have trouble getting it to not error. I want to get the response.content to a global variable to be use later, but I couldnt get it to not error, so the only way I can get it to run successfully only with console.write above, but it still return empty.
all the example or questions/answered about this seems to be simple only like that. But why mine always return empty ?
please help.
oh and please give me the answer and example in vb.net. All the other samples that I saw using c#, and I'm afraid that my trouble was because I translate it to vb.net wrong. And if can, I dont want to use async, only if it's really2 needed.
thx very much

Answer 1

ok.
this is just for future reference if somebody encounter the same problem
so I have tried all things that I found (even tried the certificate and protocol of tls12, etc), and almost gave up.
when at last, I tried to change the addparameter for grant-type to :
Request.AddQueryParameter("grant_type", "client_credentials", True)
at last I got the token after a week trying