This error comes when one tries to remap a deleted user which was deleted earlier from Client OU but existed on the Cloud OU. The following steps might help you for reaching the fix to the mentioned issue:
- Clear the value of DesktopProfile attribute for Cloud User.
- Remove Mapping of ClientAD User by removing the <OUName_Sync> group from ADUC directly OR by clicking on Licensing tab of ADSync tool and then clicking on Local AD root this way you would be able to see the list of synchronized objects details. You can remove any user from this synchronized user list.
- Then remap the User from : CloudAD Settings tab of ADSync utility.
After this as soon as the next sync interval would come the new client user would automatically map with the
CloudAD account and would not prompt you for any error.