In most of the cases, the connection problem is directly related to the COM port and the connection between the GPS device and the computer where CApn Voyager is installed. The best way is to start Capn Voyager Mosaic, then access the settings menu, especially the connection settings. Switch to another port and initiate a new connection or attempt to use the device again.
Additionally, go to Device Manager and check the presence of the driver for the Furuno GPS. If it's not installed properly, any connection to and from the device will be impossible to make. Right click the problematic driver and select Update Driver.