When migrating from a different platform to Shopify, it's necessary to transfer customer information to Shopify as well.

However, merely adding an account to the Shopify admin settings for customer information doesn't automatically create a customer account.

In this case, customers need create a new account using the same email address that was added to the customer information.

(The accounts are not made in Shopify after being added by the store owner, as the customers must set their own passwords.)

By clicking on more actions on the upper right corner of the customer account page, you are able to send an account invite to create an account with the email on the customer page.

For further information about customer migration, please refer here.