Migration from cPanel to Plesk error: Unable to create FTP account: You specified incorrect username john.doe_example.com

Symptoms

• The following errors are found while migrating from cPanel to Plesk:

  CONFIG_TEXT: Login of FTP user 'john.doe@example.com' does not conform to Plesk rules. It was changed to 'john.doe_example.com'.
  Plesk restore report problem:
  Failed deployment of ftpuser john.doe_example.com (domain example.com)
  Plesk restore report problem:
  Execution of /usr/local/psa/admin/plib/api-cli/ftpsubaccount.php --create john.doe_example.com -domain example.com -passwd '' -home public_html/me-trans.ro/Ionel.oprea -ignore-nonexistent-options failed with return code 1.
  Stderr is
  Unable to create FTP account: You specified incorrect username.
  Subscription cannot be completely synchronized with service plan: the plan has some features enabled which
  can not be activated because some components are not installed. To see which components are missing and how to
  resolve that issue, try to synchronize subscription with service plan in Plesk Panel:
  login to Plesk Panel as administrator, click on subscription, then in "Account" box click "Sync" link.

Cause

Dots symbols in the FTP username ("."), or the user name starts with a capital letter, which is not allowed in Plesk.

Resolution

Rename the FTP login on the cPanel side or migrate and create a new user on Plesk after migration.

Note: It is allowed to use lowercase alphanumeric, dash, and underscore symbols in the username. The username should start with a lowercase alphabetic character and should be between 1 and 32 characters in length.