Why is guest checkout disabled or looping back to login?

Guests getting bounced to login or stuck in an email-step loop is usually a config flag (Allow Guest Checkout off, or per-website scope), a customer-group restriction, or a session/cookie issue that loses the guest cart. We check the checkout config at the right store scope, confirm the guest cart persists across steps, and fix whatever is forcing the login redirect, then test a full guest order.