Invoices send but order confirmation emails don’t. Why?

This split usually means the issue is specific to one email type, not the transport. Likely causes: the order confirmation template is disabled or points at a deleted custom template, Sales Emails > Order is toggled off while invoice/shipment stay on, or the order template has a broken directive, an adjacent }}{{depend, a nested {{depend}}, or a {{var}} not in the whitelist, which makes that one template silently fail. We isolate the affected type, fix the template/config, and confirm a real order triggers all three emails.