Hello:

I'd suggest following the advice in the other post you've created.

https://mmmcommerce.com/F...t-order-goes-through

I'd suggest reviewing all of your payment provider settings using the documentation article below, and also re-test using the _default viewset to ensure that any customizations in the viewset isn't getting in the way.

https://hotcakescommerce....oting-Payment-Issues

https://hotcakescommerce....Using-PayPal-Express

I clicked reply too soon...

When you checkout using PayPal Express, you're taken to PayPal's website where the transaction is completed, and presumably, the other goes through successfully. Then, PayPal is supposed to return you to the originating website, where in Hotcakes Commerce, there's a final step of confirming the remaining order details. In most cases, this is because shipping information may need to be verified. Once this is done the API is used for final reconciliation to potentially update the final order amount (e.g., shipping is more or less expensive after the address is confirmed).

It is at the 'final step' where I click 'Place Order', but the page just reloads exactly the same. On the backend the order does go through and payment is made successfully. The only error happens after the end user clicks 'Place Order' a second time.

The Event Logs on the site are clear other than the second button click. The 'Order Details' show no errors at all.

I'm at a loss... I have gone through the troubleshooting in the two links you sent. My installation is Hotcakes 3.5 on DNN 9.10.0. I am using the default DNN Xilion theme for the Hotcakes pages and I have no custom viewsets.