Hi,
your migration failed and you cannot continue or try to repair, since the import has not been done.
- Modify your local security policy and add the account to
'Impersonate a client after authentication' and 'Replace a process level token'.
- Uninstall DP 8.10
- Install DP 6.21 from scratch
- Import the IDB (if you have done an export before), otherwise import the media with you IDB backup and restore it
- Start again with the migration and keep in mind to "run as admin".
Best regards
Daniel