Marc,
Users and roles must be imported separately. The .archive file (or .BIMProject) contains only the project related database files. So if you have e.g. a BIM Server 21, then open its browser based Manager interface, navigate to the Users/Roles page and export these, then import them into your BIMcloud Basic. Also if you used custom access entries for a project, you must set these manually.
Best regards,
Istvan
István Moharos
Manager, Technical Services
GRAPHISOFT