Paypal Express Checkout超时处理请求

Does anybody encounter this problem in Paypal integration in PHP?

Error : Timeout processing request

Array
(
    [TIMESTAMP] => 2015%2d07%2d20T07%3a54%3a00Z
    [CORRELATIONID] => 8375b493de498
    [ACK] => Failure
    [L_ERRORCODE0] => 10001
    [L_SHORTMESSAGE0] => Internal%20Error
    [L_LONGMESSAGE0] => Timeout%20processing%20request
)

I don't know what seems to be the problem.

Thanks in advance!

There are a lot of different reasons for timeout responses:

A timeout situation occurs if an API operation's completion status is not known or the buyer navigates away from the page that receives the response before PayPal completes the operation. You must not ship goods before receiving a valid transaction ID, which indicates that PayPal accepted the payment.

From Express Checkout Getting Started Guide on PayPal Developer

Another reason for a timeout is if you are attempting a recurring payment and missing a parameter, such as an optional transaction amount: Express Checkout Recurring Payments Guide