Linking error
The most common error you will find is an error in the linking of a product within an order.
To solve it we must edit the item in the icon that appears in the Items section, as you can see in the image.
In the column that appears, you can choose in the dropdown the product that you have to link (which appears at the top of the dropdown), the one that the customer of that order has purchased.
If the item in the order is a pack, you will have to check the Link to Pack box, as shown in the image, in order to find the pack you want in the drop-down menu.
In either of the two options, either in a single product or in a pack, you have the option to replicate the linking in the other orders. If you check this option, the product will be linked in all the orders that have an error with that product and, in addition, it will be automatically synchronized in the product list.
Payment method error
This error appears when an order does not have a payment method assigned.
To solve it we must edit the payment method in the icon that appears in the Shipping Information section, as you can see in the image.
A drop-down menu will appear from which we can choose the payment method we want to assign to the order.
Once selected, click "Save" to update the payment method of the order.
How to solve rare errors
Error when processing fulfillment
To solve this problem, read this article.