Error: client and server signatures do not match

[MarkQB]

Good morning to all. I need help in finding the solution to this error.
I am building integration with ShopSite.com. They have an API.
The sample code given is in PHP code.
I don't know PHP, but I have tried and successfully generated the access_token (Step 1)
Now I am trying to download the orders and getting this below error

{
"error": "access_denied" ,
"error_descript ion": "client and server signatures do not match"
}

Below is my C# code:

string DownloadOrders()
        {
            Random random = new Random();
            string secretKey = "D054-134B-9959-3FB2";
            string token = "MTY0NzUwMTIyOHx3b29kcGFydHN8NnxGaXNoYm93bHw3NzF8";
            string downloadUrl = "https://www.example.com/cgi-woodparts/sb/db_xml.cgi";
            string port = "443";
            string urlPath = "/cgi-woodparts/sb/db_xml.cgi";
            string nonce = random.Next(123400, 9999999).ToString();
            Int32 unixTimestamp = (int)DateTime.UtcNow.Subtract(new DateTime(1970, 1, 1)).TotalSeconds;

            StringBuilder signatureBuilder = new StringBuilder();
            signatureBuilder.Append(token).Append(Environment.NewLine);
            signatureBuilder.Append(unixTimestamp).Append(Environment.NewLine);
            signatureBuilder.Append(nonce).Append(Environment.NewLine);
            signatureBuilder.Append(Environment.NewLine);
            signatureBuilder.Append("POST").Append(Environment.NewLine);
            Uri myUri = new Uri(downloadUrl);
            string domain = myUri.Host;
            signatureBuilder.Append(domain).Append(Environment.NewLine);
            signatureBuilder.Append(port).Append(Environment.NewLine);
            signatureBuilder.Append(urlPath).Append(Environment.NewLine);
            signatureBuilder.Append("clientApp=1").Append(Environment.NewLine);
            signatureBuilder.Append("dbname=orders").Append(Environment.NewLine);
            signatureBuilder.Append("startdate=11%2F01%2F2021").Append(Environment.NewLine);
            signatureBuilder.Append("version=14.0").Append(Environment.NewLine);

            string sSign = signatureBuilder.ToString();
            string signature = GetHMAC(sSign, secretKey);

            string orderUrl = downloadUrl;
            var client = new RestClient(orderUrl);
            client.Timeout = -1;
            var request = new RestRequest(Method.POST);
            request.AddHeader("Content-Type", "application/x-www-form-urlencoded");
            request.AddParameter("token", token);
            request.AddParameter("timestamp", unixTimestamp);
            request.AddParameter("nonce", nonce);
            request.AddParameter("signature", signature);

            request.AddParameter("clientApp", "1");
            request.AddParameter("dbname", "orders");
            request.AddParameter("startdate", "11%2F01%2F2020");
            request.AddParameter("version", "14.0");

            var response = client.Execute(request);
            return response.Content;
        }

private string GetHMAC(string text, string key)
       {
            key = key ?? "";
            using (var hmacsha1 = new HMACSHA1(Encoding.UTF8.GetBytes(key)))
            {
                var hash = hmacsha1.ComputeHash(Encoding.UTF8.GetBytes(text));
                return Convert.ToBase64String(hash);
            }
        }

Below is the PHP code I am referring

$json = json_decode($json, true);
 $nonce2 = mt_rand(10000000,99999999); # nonce for download request
 $timestamp = time();                  # UNIX time
 $token = $json['access_token'];
 $endpointurl = $json['download_url'];
 $url_stuff = parse_url($endpointurl);
 $endpoint = $url_stuff['path'];
 $domain = $url_stuff['host'];
 $protocol = $url_stuff['scheme'];
 if(isset($url_stuff['port']))
   $port = $url_stuff['port'];
 else if(strcasecmp($protocol, 'https') == 0)
   $port = 443;
 else
   $port = 80;
 
 # put the array back into an MAC-compatible string
 $imploded = "";
 ksort($data);
 foreach($data as $k=>$v) {
   $imploded .= "$k=" . rawurlencode($v) . "\n";
 }
 $imploded = trim($imploded,"\n");
 $macdigest = "$token\n$timestamp\n$nonce2\n\nPOST\n$domain\n$port\n$endpoint\n$imploded\n";
 $macdigesthash = hash_hmac("sha1", $macdigest, $secretkey, true);
 $signature2 = base64_encode($macdigesthash);
 
 $data['signature'] = $signature2;
 $data['token'] = $token;
 $data['timestamp'] = $timestamp;
 $data['nonce'] = $nonce2;
 
 $db_request = "";
 foreach ($data as $k=>$v) {
   $db_request .= "$k=$v&";
 }
 $db_request = trim($db_request, "&");
 
 $ch = curl_init();
 curl_setopt($ch, CURLOPT_URL, $endpointurl);

 curl_setopt($ch, CURLOPT_POST, true);
 curl_setopt($ch, CURLOPT_POSTFIELDS, $db_request);
 curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
 
 $downloaddata = curl_exec($ch);
 curl_close($ch);

Step 2 is explained in this picture. I have coded based on this and the sample PHP code above.
Please let me know what I have missed.



This is my first post to this forum, so kindly excuse me if I have missed any rules.