We just received the following Live Site Status Update from PayPal.
Notification: We are experiencing an issue which is affecting PayPal Payments Pro and Express Checkout on the PayPal Live Site.
Some PayPal Merchants may be experiencing a high number of 10001 Error for DoExpressCheckoutPayment and DoDirectPayment API calls
Our technical teams have been engaged and are actively troubleshooting the issue.
Sent Sep 1, 2016 03:51 PM CDT by ASH
Questions? Please contact PayPal Merchant Technical Services by filing a ticket; refer to PP-LIVE-7463
You can always check the live PayPal status on their blog here.