Plesk Migrator shows the the following warning on pre-migration check:
PLESK_INFO: There is no shared IPv6 address on target Plesk. Fix Plesk configuration so there is at least one shared IPv6 address
The IPv6 address is assigned to a domain on the source server, but there is no IPv6 address on the destination server.
On the destination server, add an IPv6 address in Plesk at Tools and Settings > IP Addresses.
On the source server, set an IPv6 address to None for a domain at Domains > example.com > Web Hosting Access.