URL Not Returning Data Delphi Indy TIdHttp - delphi

Question

I am trying to access a URL in Delphi using a TIdHTTP Indy Tool.
I have done the following:
Set Accept Cookies = True
Set Handle Redirect = True
Added a TIdCookieManager
http://sms.saicomvoice.co.za:8900/saicom/index.php?action=login&username=SOME_USERNAME&password=SOME_PASSWORD&login=login
The Post request works and it returns the HTML. The problem is it doesn't return the correct HTML (See Image Below).
If I take that URL ( Filling in the username and password ) and paste it into my browser exactly The Same as my Delphi Application would then logs into the correct website. But as soon as I do it with my Delphi App it returns the HTML for the login page.
The request is supposed to be executed timeously in a TTimer in Delphi.
Can anyone lead me unto the right path or point me in a direction as to how I can solve this problem ?
Some Additional Information
WriteStatus is a Procedure That writes output to a TListBox
BtnEndPoll Stops the timer
Procedure TfrmMain.TmrPollTimer(Sender: TObject);
Var
ResultHTML: String;
DataToSend: TStringList;
Begin
Inc(Cycle, 1);
LstStatus.Items.Add('');
LstStatus.Items.Add('==================');
WriteStatus('Cycle : ' + IntToStr(Cycle));
LstStatus.Items.Add('==================');
LstStatus.Items.Add('');
DataToSend := TStringList.Create;
Try
WriteStatus('Setting Request Content Type');
HttpRequest.Request.ContentType := 'text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8';
WriteStatus('Setting Request User Agent');
HttpRequest.Request.UserAgent := 'Mozilla/5.0 (Windows NT 5.1; rv:2.0b8) Gecko/20100101 Firefox/4.0b8';
WriteStatus('Posting Request');
ResultHTML := HttpRequest.Post(FPostToURL, DataToSend);
WriteStatus('Writing Result');
FLastResponse := ResultHTML;
WriteStatus('Cycle : ' + IntToStr(Cycle) + ' -- FINISHED');
LstStatus.Items.Add('');
Except
On E: Exception Do
Begin
MakeNextEntryError := True;
WriteStatus('An Error Occured: ' + E.Message);
If ChkExceptionStop.Checked Then
Begin
BtnEndPoll.Click;
WriteStatus('Stopping Poll Un Expectedly!');
End;
End;
End;
End;
* Image Example *

Answer 1

HttpRequest.Request.ContentType := 'text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,/;q=0.8';
That is not a valid ContentType value. That kind of value belongs in the Request.Accept property instead. It tells the server which ContentTypes the client will accept in the response.
ResultHTML := HttpRequest.Post(FPostToURL, DataToSend);
You are posting a blank TStringList. Putting a URL into a browser's address bar sends a GET request, not a POST request, so you should be using TIdHTTP.Get() instead:
ResultHTML := HttpRequest.Get('http://sms.saicomvoice.co.za:8900/saicom/index.php?action=login&username=SOME_USERNAME&password=SOME_PASSWORD&login=login');
You would use TIdHTTP.Post() if you wanted to simulate the HTML webform being submitted to the server (since it specifies method=post), eg:
DataToSend.Add('username=SOME_USERNAME');
DataToSend.Add('password=SOME_PASSWORD');
DataToSend.Add('login=Login');
ResultHTML := HttpRequest.Post('http://sms.saicomvoice.co.za:8900/saicom/index.php?action=login', DataToSend);