Current problem
Billing does not function if Stripe managed payments are on. The Stripe API says
Managed Payments handles taxes for you. automatic_tax[enabled] must be true when Managed Payments is enabled. Omit this parameter or pass automatic_tax[enabled]=true. Managed Payments is enabled by default on your account, but you can disable it for this request by passing in managed_payments[enabled]=false. You can configure whether Managed Payments is enabled by default at removed. See https://docs.stripe.com/payments/managed-payments/update-checkout#remove-unsupported-parameters for more details.Proposed change
Please pass automatic_tax[enabled]=true if stripe managed payments are on