Needs to redirect users on UNPROCESSABLE_ENTITY > PAYER_ACTION_REQUIRED - No checkout possible

Maybe the reason for paypal to check again could be different order totals in the cart (because no shipping could be calculated yet) and checkout (with shipping collected)? Any other ideas why PayPal might ask for confirmation?

Regular checkout, not using the Checkout buttons in cart, selecting PayPal as regular payment method, works correctly!

This is no longer fresh for me, would be great if you could investigate and report back.

Yeah I'll try to do my best, first I'd like to find out the root cause - sadly PayPal returns no details, why it wants re-confirmation. It doesn't only happen for my PayPal account (thought maybe rate limit for my tests), but any PayPal account using the Smart Checkout buttons.

Should you have any idea, please let me know.

Here's the ERROR returned:

{
   "name":"UNPROCESSABLE_ENTITY",
   "details":[
      "@""issue":"PAYER_ACTION_REQUIRED",
      "description":"Payer needs to perform the following action before proceeding with payment."
   ],
   "message":"The requested action could not be performed, semantically incorrect, or failed business validation.",
   "debug_id":"0e90efd2abb2d",
   "links":[
      "@""href":"https://developer.paypal.com/api/rest/reference/orders/v2/errors/#PAYER_ACTION_REQUIRED",
      "rel":"information_link",
      "method":"GET",
      "@""href":"https://www.paypal.com/checkoutnow?token=XXXXXXXXXXXXXXX",
      "rel":"payer-action",
      "method":"GET"
   ]
}

@jsacksick do you know any project where Show Smart Payment Buttons on the cart page is working in production and Checkout completes correctly?

I really can't get it working due to the response from PayPal given above. Regular checkout works, but sadly the message from PayPal doesn't explain any details why the user needs to re-confirm the order.
I already tried pre-calculating the total amount, as I thought maybe the problem is that the final amount is different, but it still fails with the same error.
Furthermore I'm not sure how we should implement that redirect then, because it wouldn't be nice to redirect the main page, I think?
Guess typically that's done in the popup.

But first I'd really like to know what's this caused by and if it works somewhere. Maybe we can circumvent this problem...