Pressing the ‘Pay for Invoice’ button from an invoice page results in a blank page and a 503 error in the log.
Paypal Standard (Sandbox mode) is configured in the admin:
For invoice url: https://portal.theassociationpartner.net/wpi_invoice/inv-1199/
The invoice displays correctly. Pressing the ‘Pay for Invoice’ button redirects to: https://portal.theassociationpartner.net/wpi-checkout/?wpi_action=pay_for_invoice&invoice_key=79777523ea65efe8d5eef12b8b0d9318 which displays as a blank page with a 503 error. Note that this happens regardless of the Payment Gateway selected (tried PayPal & Test Payment).
Removing the invoice_key parameter from the url after receiving the blank page results in the checkout page being displayed. The error ‘Error: You are not allowed to view this invoice’ appears above the ‘Proceed to PayPal’ button.
The ‘Proceed to PayPal’ button redirects to PayPal correctly.