FYI for others (Feature errors saying 'Double Authentication is not implemented' [Technical Documentation Publishing])

Aras.ConversionFramework.Exceptions.EventCallbackErrorException: See inner exception for details: ---> System.Exception ---> System.ServiceModel.FaultException: Double authentication is not implemented

The solution, in my case, was the user record's configured vault was set to one that is used for another aras server. Therefore it may have been the cause for that. After swapping them to the correct server, then it was working for them!