The user account that is generating the error must be examined in Microsoft Active directory, Users and Computers.
Checking "effective permissions" on that account and the permissions of the service account on that user.
It could be a lack of inheritance or active deny on the account. All of this is outside of Password Manager and exclusively in the realm of Microsoft and Active directory. For further information, see the following Microsoft KB article:
Check that the service account as full read/write permissions on the Comment attribute as well as permissions to reset password.
All of the permissions listed here: