Starting with Jet Essentials 2015, data sources for Microsoft Dynamics NAV's Web Services can use Office 365 authentication (also known as "OAuth authentication").
OAuth allows a Dynamics NAV installation to support "single login" capabilities.
If your installation of Dynamics NAV uses this type of authentication, you can use Jet Essentials' Office 365 authentication to access your NAV data.
You will need to contact your Dynamics NAV system administrator to obtain the settings necessary for your organization.
Administrators will want to see the article Configuring Office 365 Authentication for Dynamics NAV