Coupons Cause PayPal Smart Checkout Errors

Hi there! I’m a happy long time user of the plugin. Today I noticed an issue on my site while doing some PayPal sandbox testing. When testing a percent off coupon it causes a paypal error due to incorrect formatting of the currency or amount.

Details:
Error message from PayPal:

“name”: “VALIDATION_ERROR”,
“details”: [
{
“field”: “transactions.amount”,
“issue”: “Currency amount must be non-negative number, may optionally contain exactly 2 decimal places separated by ‘.’, optional thousands separator ‘,’, limited to 7 digits before the decimal point and currency which is a valid ISO Currency Code”

– This happens in both Firefox and Google Chrome browsers. Haven’t tested other browsers.
– I’m using PayPal Smart Checkout with PayPal standard disabled
– I’m using USD currency with $ as the currency label in settings.
– I’m using and have tested only single digit and double digit “Percent off” coupons with no expiration date. I.E. 5% off, 10% off.
– Coupons work correctly and the discount is correctly calculated and shown in the customer cart.
– When a user clicks to checkout with Smart Checkout, the checkout process crashes with the error message shown above.

I’m not sure when this issue started but I do know coupons have worked fine in the past on the site. (Customers have used them.) I think it was before I enabled PayPal Smart Checkout but I’m not sure.

At first glance it looks like perhaps the plugin is incorrectly formatting the currency amount when a coupon is used, at least in the eyes of what PayPal Smart Checkout is expecting and seeing?