The button is only shown when your kitchen location has a Stripe account ID and a live secret key. If the location is still on test-mode keys (used during setup) the panel is read-only, and any attempt to save returns "Invalid Keys". Complete live onboarding on Stripe > Connect so the location shows as connected; the button appears afterwards. Saving can also fail with "Invalid Permissions!" (your role lacks Stripe Account Settings) or "Invalid Account" (the page was opened for a different location than the one being saved - reload and try again).