Unknown payment method

method must be one of the enumerated values — promptpay, truemoney, linepay, shopeepay, bank_transfer, direct_debit, installment. This error is the enum check, not the "is it enabled for you" check, which is payments.attempt_not_allowed.

What to do

Take the value from the enum in the reference rather than from a display string. "PromptPay", "prompt_pay" and "qr" are all this error.