.NET Framework 4.8集成DocuSign JWT认证获取AccessToken报错

我正尝试在.NET Framework 4.8的Web应用中集成DocuSign，使用DocuSign eSign dll版本6.5.0。通过JWT授权方式获取Access Token，已在DocuSign开发者门户创建应用和集成密钥，并完成授权操作。

但获取Access Token时抛出ApiException异常，提示信息：

Error while requesting server, received a non successful HTTP code with response Body:

对应代码实现：

getAuthInfo(out string clientID, out string rsaPrivateKey, out string impersonatedUserID);

var docuSignClient = new DocuSignClient();

var scopes = new List<string>{"signature","impersonation"};

var privateKeyBytes = Encoding.ASCII.GetBytes(rsaPrivateKey);

try
{
    var authToken = docuSignClient.RequestJWTUserToken(
                        clientID,
                        impersonatedUserID,
                        "account-d.docusign.com",
                        privateKeyBytes,
                        1,
                        scopes);
                        
    return authToken;               
}
catch (ApiException apiExp)
{
    // Consent for impersonation must be obtained to use JWT Grant
    if (apiExp.Message.Contains("consent_required"))
    {
        
    }
}

更新内容1 #

安装了eSign dll版本6.2.0（与已验证可用的快速启动控制台版本一致），同时修改DocuSignClient的实例化方式，传入开发环境URL配置：

getAuthInfo(out string clientID, out string rsaPrivateKey, out string impersonatedUserID);

var config = new DocuSign.eSign.Client.Configuration("https://demo.docusign.net/restapi");
var docuSignClient = new DocuSignClient(config);

var scopes = new List<string>{"signature","impersonation"};

var privateKeyBytes = Encoding.ASCII.GetBytes(rsaPrivateKey);

try
{
    var authToken = docuSignClient.RequestJWTUserToken(
                        clientID,
                        impersonatedUserID,
                        "account-d.docusign.com",
                        privateKeyBytes,
                        1,
                        scopes);
                        
    return authToken;               
}
catch (ApiException apiExp)
{
    // Exception Message: "Error while requesting server, received a non successful HTTP code with response Body: "
}

更新内容2 #

string directoryPath = Server.MapPath("~/App_Data/");
string fileName = "private.key";
var filePath = Path.Combine(directoryPath, fileName);
var privateKeyBytes = File.ReadAllBytes(filePath);

try
{
    var accessToken = JWTAuth.AuthenticateWithJWT("ESignature", ConfigurationManager.AppSettings["ClientId"], ConfigurationManager.AppSettings["ImpersonatedUserID"],
                                                    ConfigurationManager.AppSettings["AuthServer"], privateKeyBytes);
}
catch (DocuSign.eSign.Client.ApiException apiExp)
{
    // Exception: Error code 500
}

此时抛出ApiException异常，错误码为500。

内容的提问来源于stack exchange，提问作者Pavel