After selecting the list button on ScanLister, you must wait for the upload to complete before proceeding. Typically this will take 5 minutes. However, in some cases, this can take longer.
To check the upload status on your Amazon Seller Account, go to Inventory - Add Product via Upload - Monitor Upload Status.
You will then see the screen below.
When your batch says, "Upload Status Done", you can the proceed to the next step. If you are an FBA seller, you can now create your shipping plan.