If you get the following error message…
“STRIPE: Error creating session for checkout: Invalid currency options ‘usd’.
The payment method ‘alipay’ only supports the following currencies: ‘cny’, ‘eur’.”
… then there is a problem with your currency configuration in Stripe.
In the case above, the main currency of your Stripe account and your bank account is probably EUR, but you entered USD as currency in ConfTool. Now Stripe would have to exchange payments via Alipay twice: First from CNY to USD (as Alipay only supports CNY) and then from USD to EUR.
However, there is a workaround in ConfTool for this problem.