L_ERRORCODE0 => 11813-无效的回调URL。贝宝（Paypal）在沙盒测试帐户上正常使用付款，但未启用

我在使用贝宝（Paypal）API和重新付款时遇到问题。我已经有可以使用的沙箱测试帐户：

define('API_USERNAME', 'API-USERNAME');
define('API_PASSWORD', 'API-PASSWORD');
define('API_SIGNATURE', 'API-SIGNATURE');
define('API_ENDPOINT', 'https://api-3t.sandbox.paypal.com/nvp');
define('PAYPAL_URL', 'https://www.sandbox.paypal.com/webscr?cmd=_express-checkout&token=');
define('PAYPAL_ENVIRONMENT', 'sandbox');

但是，当我尝试添加实时凭据时，单击结帐后只能看到错误：

define('API_USERNAME', 'API-Username');
define('API_PASSWORD', 'API-PASS');
define('API_SIGNATURE', 'API-Signature');
define('API_ENDPOINT', 'https://api-3t.paypal.com/nvp');
define('PAYPAL_URL', 'https://www.paypal.com/cgi-bin/webscr?cmd=_express-checkout&token=');
define('PAYPAL_ENVIRONMENT', 'live');

现在，当我单击以结帐时，网站向我显示错误：

SetExpressCheckout failed: Array
(
    [TIMESTAMP] => 2014%2d02%2d01T11%3a53%3a32Z
    [CORRELATIONID] => 4caf5dc7552f2
    [ACK] => Failure
    [VERSION] => 98%2e0
    [BUILD] => 9285531
    [L_ERRORCODE0] => 11813
    [L_SHORTMESSAGE0] => Callback%20URL%20is%20wrong%20type%2e
    [L_LONGMESSAGE0] => Callback%20URL%20is%20wrong%20type%3b%20you%20must%20use%20the%20HTTPS%2e
    [L_SEVERITYCODE0] => Error
)

我将很高兴为您提供任何帮助！非常感谢