["[Code:8560] [Error]SKU 12345, Missing Attributes unit_count. SKU 12345 does not match any ASIN. Creation of a new ASIN requires the following missing attributes: unit_count. Feed ID: 0. For details, see http://sellercentral.amazon.com/gp/errorcode/200692370"]
If you see this error returned, you would need to check first the Amazon Main XML Mapping settings in the Channels tab and see whether the Unit Count field is mapped to any existing custom field. If there isn't any custom field mapped to it and if there isn't any other custom field like ItemPackageQuantity which would typically contain the same or similar value and that you can map it to, then you would need to create a new dedicated custom field and then map it to Unit Count so you can then add the required value and re-submit the item to Amazon for processing.