N-Genius付款网关集成错误

Question

这是用于获取我正在使用的访问令牌的代码，但得到的响应为“不可访问” 帮我解决这个问题

var client = new RestClient("https://api-gateway.sandbox.ngenius-payments.com/identity/auth/access-token");
            var request = new RestRequest(Method.POST);
            request.AddHeader("accept", "application/vnd.ni-identity.v1+json");
            request.AddHeader("Authorization", "Basic "+ Apikey);
            request.AddHeader("Content-Type", "application/vnd.ni-identity.v1+json");
            request.AddParameter("application/vnd.ni-identity.v1+json", "{\"realmName\":\"ni\"}", ParameterType.RequestBody);