Why am I getting the error "To proceed with your payment, please accept the payment plan for your subscription by ticking the box" when subscribing to XER Toolkit?

[Chrisg]

This error usually occurs because the required payment plan checkbox has not been selected.

To complete your subscription, make sure to tick the box that says:
“I allow XER Limited to debit the due amounts on a recurring basis according to the selected subscription above and to store my payment details for this purpose.”

If this box is not ticked, the system cannot process your payment. Double-check that you have selected it before clicking “Subscribe.”