You should only ship orders that you can verify in the Manage Orders tool in your seller account. Ask the buyer for an Order ID. If you cannot locate the Order ID in Manage Orders, then refer the buyer to Amazon Customer Service.
Here are some causes and possible solutions for why you may not be receiving your Sold, Ship Now email notifications:
The connection between the Amazon mail server and your mail server timed out, or your Internet service provider (ISP) was temporarily unable to receive messages.
Contact your ISP to ensure that there are no problems with your account.
Confirm that your ISP is not filtering emails from Amazon.
Your email address is incorrect or your inbox was full.
Verify that your contact information is correct in Account Info (on the Settings menu).
Be sure to maintain your primary selling account mailbox so you receive all messages from Amazon.co.jp. If your inbox is full, then emails cannot be delivered.
Email filtered or discarded
Your email service identified the message as spam or junk.
Check your Junk and Trash folders for the missing Sold, Ship Now emails.
Check any spam filters or rules you have that may inadvertently filter out these emails.
Add email@example.com your contacts list.