You will get no readings with a meter on a good TVS diode, they will appear to be open in both directions. The exact size of the package is not significant as long as it has the right ratings.
What computer O/S do you run? For Rev. L TIU's, I just fire them up and run with them for Windows 10. What you describe sounds like an issue with the USB drivers.
Did you open Device Manager and check to see if your adapter cable is recognized? I have a serial port card, so ignore COM4 and COM5. I plugged my Vantec USB To Serial Adapter (CB-USB20SR) adapter in and it shows up as COM11. I use this with my laptop for older TIU's and for the Legacy command base communications.