Internal server error, trying to pay for an order

[elitu]

Hi, i'm trying to pay for order id : 852805636S286194K for the payer id

GLGJLKYWHX6LW

via 

https://api.sandbox.paypal.com/v1/checkout/orders/852805636S286194K/pay

I'm getting : 

"{\"name\":\"INTERNAL_SERVICE_ERROR\",\"message\":\"The server encountered an internal error that prevented it from fulfilling this request.\",\"information_link\":\"https://developer.paypal.com/docs/api/#INTERNAL_SERVICE_ERROR\",\"debug_id\":\"54d1066a8e14\"}"

Please help.