Catalina - USB Serial Cables seem to be broken
Just FYI, I have the same problem. Using Fusion it will work on e.g. a virtual Windows Machine. 

Another user has also posted this, but no replies on that thread. It appears to be a more general problem.

Update: I've been working on this for some days, but it might be working now. I am not quite sure what did the trick, however. 

I've installed/reinstalled the VCP driver found here. That didn't help. 

Then I also installed the D2xxHelper, which also didn't help. Actually it made it worse since this actually removed the device completely from /dev/cu.usbserialxxx. 

I then rebooted the Mac and the device was back and now actually working as it should. If it was necessary to install both or only one of the two and reboot, I do not know. Hope this helps you too.