Actually we have solved the issue via PM 8)
In general
- if user deletes his my avast account while password synchronization is turned on then data are lost and it can’t be recovered!
- if user just removes device from avast account, while he was synchronizing passwords and he has no other device which can authorize new devices for synchronization he still may use self-authorization feature by following this guide: https://www.avast.com/faq.php?article=AVKB92