Our system had a brief glitch around 7:30pm PDT/MST tonight, lasting about 50 minutes. We caught and fixed problem promptly as it cropped up, although this brief window may have affected a few downloads (causing them to fail or be inaccessible) and cart checkouts, apparently just those using a Discount Code (resulting in a "cart validation error").
You may need to use your Seller Admin > "Re-activate expired links" or "Send free download link" to ensure affected buyers can get the full count of download attempts you allow for their product.
We do sincerely apologize for the inconvenience.