In order for Jet Reports to connect to your Dynamics NAV data base through NAV Web Services (also known as "SOAP Services"), SOAP must be enabled for the NAV Server Instance that is being accessed.
Otherwise, you will need to use the Dynamics NAV Administration tool to enable SOAP.
Enabling SOAP Services
After starting the Dynamics NAV Administration tool for your version of NAV:
In the left pane, expand the Microsoft Dynamics NAV Server name
Note: unless you are administering a remote computer, this is Microsoft Dynamics NAV (local).
Under the Server name, select the Instance you need to modify
In the center pane, expand the SOAP Services section. If Enable SOAP Services is not checked, click the Edit button
Check Enable SOAP Services, and then click the Save button.
Ensure that the other settings in this section are configured correctly (see MSDN article Configuring Microsoft Dynamics NAV Server)
Finally, you will need to restart your Dynamics NAV Instance for the changes to take effect.