Migration completed with a warning:
Protected directory 'plesk-stat' of domain 'example.com': login of protected directory user 'test.user' does not conform to Plesk validation rules. Login was changed to 'test_user'.
Plesk migrator changes protected directory user name if it contains a dot symbol on the source server. This is an internal issue with ID #PMT-3317, which is planned to be fixed in future product updates.
This warning can be ignored with the note that the login for webstat page was changed.
Alternatively, the login for accessing domain's webstat page can be changed back to 'test.user' for the migrated domain in Domains > example.com > Hosting Settings