Different webhook errors in different environments - Webhook URL does not meet the requirements



I have some problems with registering a new webhook endpoint.

When I try to register a webhook on my test environment ( https://twitter.*******.com/mazlum/webhook), altough I am receiving a crc_token challenge and respond with a valid token, I get this error for the register request :

{“errors”:[{“code”:214,“message”:“Webhook URL does not meet the requirements. Please consult: https://dev.twitter.com/webhooks/securing”}]}

        using (var crypt = new HMACSHA256(Encoding.UTF8.GetBytes(pConsumerSecret)))
            var encoder = new ASCIIEncoding();
            byte[] crypto = crypt.ComputeHash(encoder.GetBytes(pCrcToken));
            response = Convert.ToBase64String(crypto).TrimEnd('=', '\r', ' ', '\t'); 

When I try to register the same webhook by encoding the uri address on my test environment( https%3a%2f%2fmconfig.*********.com%2fmazlum%2fwebhook), I get a new error : {“errors”:[{“code”:32,“message”:“Could not authenticate you.”}]}

Do you have any comment?

Best Regards