Paypal did not notify me in advance that I would not be able to use the instant transfer. It seems to be something that is not readily available. You can use it for XXXX transaction and then when you make an identical transaction for the same amount to the same person the next month, you are not able to complete, but the following month you can. A search on google implied that it could be due to an credit card coming up for expiration but offered no other reasons for when that is not the case - and by the way these are not answers from paypal but from other consumers. 
