Hello, the payment page needs the line items formatted in a certain way. So you navigate to the Connect tab, then on this page you’ll edit the line item example and
Create an invoice with the Order Line Items (Column 1 = Name, Column 2 = Quantity, Column 3 = Price), then create a line item (Orange, 5, 5) and click “build link”. This saves the line-item configuration for future links.
Please try out the first suggestion and that should resolve it, the connect tab will generate a link and then the page automatically knows the proper formatting after that. Lastly it’s helpful to review the URL generated by the plugin, even yourself may find an issue such as a % or any character that escaped the required format for the HPP URL