403 Forbidden on REST API Upload to spaces

Question

Have been trying to upload files using HTTP PUT requests in C#. The environment I am using Digitalocean Spaces is in Unity. The SDK for unity/C# is quite unstable in Unity. As in it will work for a platform, but can fail completely in a different platform. As a result just trying to get basic http requests to work. I also tried generating many different keys (so the access key and secret are definitely correct). The requests do work fine in postman. But postman I’m not sure how postman signs the request headers. Here is my code so far. What am I doing wrong?

public void RestAPI()
{
    byte[] fileBytes = File.ReadAllBytes(filePath);

    // Calculate the content length
    long contentLength = fileBytes.Length;

    // Calculate the content SHA-256 hash
    string contentSha256 = ComputeSHA256Hash(fileBytes);

    // Prepare the URL and object key
    string objectKey = "testFile.png"; // The key (name) for your object in the Space
    string url = $"{endpointURL}/{bucketName}/{objectKey}";
    string contentType = "application/octet-stream";
    string acl = "x-amz-acl:private";
    // Get the current date in UTC format
    DateTime now = DateTime.UtcNow;
    string amzDate = now.ToString("yyyyMMddTHHmmssZ");
    string dateStamp = now.ToString("yyyyMMdd");
    var hostName = endpointURL.Replace("https://", "");

    // Create the canonical request
    string canonicalRequest = $"PUT\n/{bucketName}/{objectKey}\n\nhost:{hostName}\n" +
                              $"x-amz-content-sha256:{contentSha256}\nx-amz-date:{amzDate}\n\n" +
                              "host;x-amz-content-sha256;x-amz-date\n" + contentSha256;

    // Create the string to sign
    string stringToSign = $"AWS4-HMAC-SHA256\n{amzDate}\n{dateStamp}/{regionSlug}/s3/aws4_request\n" +
                          ComputeSHA256Hash(canonicalRequest);
                                  // Generate the signing key
    byte[] signingKey = GetSignatureKey(secretKey, dateStamp, regionSlug, "s3");

    // Calculate the signature
    byte[] signatureBytes = HmacSHA256(signingKey, stringToSign);

    // Convert the signature to hexadecimal
    string signature = BitConverter.ToString(signatureBytes).Replace("-", "").ToLower();
        HttpClient client = new HttpClient();

    ByteArrayContent contentBinary = new ByteArrayContent(fileBytes, "application/x-www-form-urlencoded");

    contentBinary.Headers.Add("Content-Length", contentLength.ToString());
    contentBinary.Headers.Add("Authorization", $"AWS4-HMAC-SHA256 Credential={accessKey}/{dateStamp}/{regionSlug}/execute-api/aws4_request, " +
                                               $"SignedHeaders=host;x-amz-content-sha256;x-amz-date, Signature={signature}");
    contentBinary.Headers.Add("x-amz-date", amzDate);
    contentBinary.Headers.Add("x-amz-content-sha256", contentSha256);
    contentBinary.Headers.Add("Host", $"{hostName}");
    contentBinary.Headers.Add("Connection", "keep-alive");

        client.Put(new System.Uri(url), contentBinary, HttpCompletionOption._AllResponseContent_, (response) =>
    {
        if (response.Exception != null)
        {
            Debug.Log(response.Exception);
            return;        }
        string responseData = response.ReadAsString();
        Debug.Log(responseData);
    });
}

private byte[] HmacSHA256(byte[] key, string data)
{
    using (HMACSHA256 hmac = new HMACSHA256(key))
    {
        return hmac.ComputeHash(Encoding.UTF8.GetBytes(data));
    }
}

private byte[] GetSignatureKey(string key, string dateStamp, string regionName, string serviceName)
{
    byte[] kDate = HmacSHA256(Encoding.UTF8.GetBytes("AWS4" + key), dateStamp);
    byte[] kRegion = HmacSHA256(kDate, regionName);
    byte[] kService = HmacSHA256(kRegion, serviceName);
    return HmacSHA256(kService, "aws4_request");
}

private string ComputeSHA256Hash(byte[] input)
{
    using (SHA256 sha256 = SHA256.Create())
    {
        byte[] hashBytes = sha256.ComputeHash(input);
        StringBuilder builder = new StringBuilder();
        foreach (byte b in hashBytes)
        {
            builder.Append(b.ToString("x2"));
        }
        return builder.ToString();
    }
}


private string ComputeSHA256Hash(string input)
**{**
    using (SHA256 sha256 = SHA256.Create())
    {
        byte[] hashBytes = sha256.ComputeHash(Encoding.UTF8.GetBytes(input));
        StringBuilder builder = new StringBuilder();
        foreach (byte b in hashBytes)
        {
            builder.Append(b.ToString("x2"));
        }
        return builder.ToString();
    }
}