I am using the following code to accept payments for digital goods:
https://www.x.com/blogs/Nate/2011/01/07/digital-goods-with-express-checkout-in-php
I have a sandbox account and I have used the API credentials from the sandbox account.
Everything works fine until I press the "Pay with PayPal" button. At this point when I try to login to continue the simulated transaction I receive the following error: "We are unable to complete your request at this time. Please try again later. We apologize for the inconvenience."
I have no idea whet I'm doing wrong, can somebody help?
There are a number of people on the X.com forums with the same issue. It appears to have been resolved for some of them by asking PayPal tech support to enable Digital Goods transactions for their sandbox account. Apparently this option is not available during normal sandbox setup.
Just in case if anyone else getting the same error.
https://www.x.com/thread/49935
Make sure you set the PaymentAction to "Sale" instead of "Authorization"
If you receive an error message in your uri request LONGMESSAGE parameter to the effect of "Your account is not signed up to sell Digital Goods" you can ask on the x.com forums to have it added.
However if you're in a hurry, you can now create a new pre-configured test user and set its type to Merchant. It will have PayPal Express/Digital Goods enabled even though there isn't a configuration option for it.
(Website Payments Pro test users will not be auto configured with Digital Goods in my experience.)
来源：https://stackoverflow.com/questions/4734718/paypal-digital-goods-error-on-login