The following error appears during migration when trying to select subscription without customer/reseller:
Warning: Execution of /usr/local/psa/admin/plib/api-cli/user.php --create email@example.com -owner admin -guid 54b90b8b-eb74-4377-a95c-4c220b5af8e7 -cname user -passwd '' -passwd_type sym -status enabled -domain-admin false -email firstname.lastname@example.org -external-email true -role Mail\ User\ 2 -legacy-user false -file-sharing-id 8fc2a7cbde10304f8f5ebe39741faed2 -subscription-name domain.tld -ignore-nonexistent-options failed with return code 1. Stderr is Error during user creation: Owner with id 1 has not subscription with id 453
This is a software issue with internal ID PPPM-1863. Fixed in Plesk 12.5
Migrate particular subscription(s) with respective owner (customer/reseller) account.