There is currently an issue at the PayPal website that is preventing orders from being processed. There seems to be a system wide issue on their end with transactions being processed and appearing in the buyer and seller accounts. A discussion thread of this issue can be seen at the PayPal forums here: https://www.paypal-community.com/t5/About-Payments/Known-Issue-Payments-not-appearing-on-sender-or-receiver-s/td-p/1002646/page/30
We are not seeing any issue on our system side, but need PayPal to post over the payment details for us to process and deliver download orders.
Update: PayPal is posting orders as normal again.