If you've elected to skip an order but change your mind, you can unskip the delivery as long as you do so before the end of the shopping window for the order.
To unskip an upcoming order:
Step 1: Log into your account
Step 2: Click "Delivery Schedule" from the "My Account" menu
On this page, you'll see a schedule of your upcoming deliveries
Step 3: Click "unskip" on the order you'd like to receive