EZ Importer: Line Item Quantity Can No Longer Be Less Than 1
As of October 28, 2018 Shopify will no longer allow you to import orders that have a line item quantity less than 1. They are making the change to ensure consistency throughout their platform as they do not allow orders with a line item quantity of less than 0 to be fulfilled.
There is no way around this so if you are trying to run an import and the quantity is less than 1 you will need to update your import file.
For more information about this validation change read the official announcement from Shopify.