gofanco offered to send me a new one but it's pretty clear that this isn't a hardware issue as clone mode works. I have downloaded the logging tool and will try to use it to debug the problem. I asked gofanco support if they knew how to use it as well. They are able to get it working on their own system so there must be a configuration or environmental issue with my setup. But it would be nice to know what the issue is.

I ran the DisplayLink diagnostic tool and it collected a bunch of information in a number of files. Unfortunately they are not human-readable so it appears that a tool is required to read them. I have sent this information to gofanco so that they can request the tool from DisplayLink or so that they can submit the diagnostic files for DisplayLink to analyze. It seems like a rather broken process.

I reread the page for the support tool. It looks like I need to turn on additional logging options and then submit the diagnostic files (they are automatically zipped up) to DisplayLink. So I'll work on doing that.