Reason: Invalid item for MSKU XX_YOUR_SKU_XX with reason NOT_IN_PRODUCT_CATALOG. - InvalidRequestException
This issue occurs when the Amazon.com information and the information provided by Amazon's MWS API are not in sync.
This is outside our control and usually remedies itself depends upon the next API sync that Amazon initiates.
If you are still having this issue after 24-hours, please contact Amazon seller central support, let them know that the item is not being found when searched via their MWS API and inquire as to when the issue will be resolved.