I re-started my laptop (after our Network Admin did some diagnostics) and now calling the program with "V4" as a version provides a better error message

The assembly is built by a runtime newer than the currently loaded runtime, and cannot be loaded.

But I am not sure what does it mean. I previously tried with the most recent version of .NET I have (full version) and it gave me yet a different error about VFP9 needed to download and install a version of framework.