Magellan Platinum help

Hi guys,
I have owned a magellan Platinum for many years.
It has run perfectly on win98 - win XP - win 7 AND I had it running perfectly on Win 8.1 which was a small 7 inch tablet as a test to see if it would work.

So my problem now is, after finding out it worked perfectly on win 8.1, I went and bough myself a surface pro 3 and installed the mapping program (discoverAus street and Tracks) The program works fine as I have opened saved files which show my old trips on the map. But As the Magellan uses a serial bus into a usb (USB 323 converter), when I go to start a trip log, it comes up with the following message..
failed to open the specified COM-port.
When I go into system and device driver, Under "other devices" I see the usb Ver1.2 device with a yellow triangle over it.
The device status says 'the drivers for this device are not installed (code28). There are no compatable drivers for this device. to find a driver click Update driver.
when I try to "update drivers" nothing happens

In the com port selection window its blank as the pro3 only runs 1 USB 3 plug.
I have no idea what else to try and am hoping someone here can help with a few things to do.

 

What driver is installed on that 7 inch tablet with Win 8.1 where your cable is working ?