Alright, everything is OK now, to those who had the same problem, after having updated your plugin, tick “No” to “Use as final checkout” when you add the “Cart/Checkout” widget cause the “Pay with LR” button on the widget won’t work but the one on the checkout page will. Thanks for fixing the issue.
I closed the dispute in PayPal (I opened it because I had no replies from you after 10 days..)