The ForNAV Designer tries to get the report object source code directly from Dynamics NAV/Business Central. It uses the finsql.exe to export the object in text format. This step requires a NAV/Business Central developer license on the NAV/Business Central server.
Because the finsql.exe uses the license on the server, it is not enough that you open C/SIDE and in the License Information window, click Change license. You must instead click, Upload license.