Most likely Amazon is missing Battery and Dangerous Goods information for a product or products that are new to your inventory. The error is produced when we try to convert it to Fulfilled by Amazon without first supplying this info.

We are working with Amazon to provide this information through the APIs but in the meantime you can Add the Product to your Inventory in Seller Central and indicate the Dangerous Good information during the Convert to Fulfilled by Amazon step.  Before you can list the product we need to sync the new MSKU from Seller Central. You can force a sync from ScanPower Settings->List.