php - Paypal Sandbox: DoExpressCheckoutPayment 10001 Internal Error -

i'm working on e-commerce website, have integrated paypal (express checkout) , worked until yesterday.

when send doexpresscheckoutpayment request, receive response :

  "ack" => "failure"   "version" => "204.0"   "build" => "000000"   "l_errorcode0" => "10001"   "l_shortmessage0" => "internal error"   "l_longmessage0" => "internal error"   "l_severitycode0" => "error" 

the parameters send :

'user' => $username, 'pwd' => $password, 'signature' => $signature, 'version' => "204.0", 'method' => 'doexpresscheckoutpayment', 'token' => $token, 'payerid' => $payerid, 'paymentrequest_0_amt' => $price, 'paymentrequest_0_itemamt' => $price, 'paymentrequest_0_paymentaction' => 'sale', 'paymentrequest_0_currencycode' => 'eur' 

do have idea ?

i solve creating new buyer , merchant account @ https://developer.paypal.com/developer/accounts both in same country (and using same currency).

i updated api credentials (username, password, signature) new merchant , payed new buyer account.