If your Microsoft Dynamics 365 Business Central Cloud solution hosted by Microsoft is authenticated via an unmanaged Azure Active Directory (AAD), then you must change the status to managed. Otherwise, your ForNAV Designer cannot authenticate and get access to the report and fields information in your Business Central Cloud.
Most full Business Central Cloud installations already run on a managed AAD. However, if you sign up for a trial with an email address that does not belong to an existing AAD, then it will create one with the unmanaged state.
To change the status of your AAD take a look here: