Stripe checkout is not enabled — add STRIPE_SECRET_KEY or save the Stripe secret key and enable Stripe checkout
Role-plan checkout refused Stripe until the secret key is available and Stripe checkout is enabled (full product wording).
Why this happens
isStripeCheckoutEnabled() false or Stripe client unavailable before creating a Checkout Session. Sibling of the short Stripe checkout is not enabled.
Diagnose and fix
1. Save the Stripe secret key in Admin → Settings → Payment Settings or set STRIPE_SECRET_KEY in env.
2. Turn on Stripe checkout; save.
3. Match test/live keys to the mode you intend; configure webhook signing secret separately.
4. Retry premium checkout with card/Stripe.