"user not exist"

I have followed every step of the email migration instructions ( https://www.zoho.com/mail/help/pop-imap-migration.html ) with success. I'm currently attempting to add my account, becky@wordsineffect.com, to complete the migration.

Unfortunately, I'm getting an error message, which says "user not exist." So migration isn't happening, and emails sent to becky@wordsineffect.com are being returned, marked "undeliverable."

Please help!