Hi,
When you restore the AOS database from 1 environment to another where there is no relation of domain or user then you will encounter above mentioned error nduring report server validation / creation of folder / making default.
Reason: Existence of records of parent server in the table SysServerSessions. though you added the new server details as record in SQL level, you needs to delete those records too.
Hope this will solve your error.
Thanks,
