This document explains why the invoice number, or order number, are not available in the order history.
Personal orders are never invoiced. They are always paid before or when you receive your order. So the Invoice Number link in the detail of your personal orders may say "No Invoice Information Available."
Some of the orders in your order list do not have an order number associated with them. Only the first line of an order has the order number to its left. You may be looking at an order line that is not the first order line. If you go up in your list to the first line showing an order number and click on that order number, you’ll be brought to the order detail for the line you want.