If the error message is similar to the following:
"internal_id : u'5cd62fd48e5211e1a792590ee29a2460'
email : firstname.lastname@example.org'
amount : u'1.00'
PayerID : u'SWMDSR2ANG3ZW'
token : u'EC-3YC00941DH4581848"
It seems that you have not been charged, or at least our system didn't receive money from PayPal or other checkout methods. The request was not processed and serials were not assigned. Please check your PayPal or other checkout records and see if you were charged. Forward us the receipt and we’ll sort it. If you do not have a receipt from PayPal or other checkout methods it means you have not been charged.