Orders marked with the red triangle icon have an invalid addresses and will need to be updated before they can be shipped. The red alert triangle will appear under the "Address Type" column and no 'C' or 'R' or 'I' will appear.
You can click the red triangle next to an order to edit the address.
If the "Address Type" column does not appear in the header bar above your orders, this column can be added using the "Arrange Columns" option. Learn about organizing column headers on the ORDERS page.