I am also using Unity Hub 2.4.2 and having issues opening any projects, though I do not get the luxury of an error message on my system. Seems this may be a common problem.
This sounds very similar to an issue I ran into. My solution was to open Unity manually. So, not Unity Hub, and not opening a project. Just open the Unity 2019.10f2 file or shortcut. This will probably prompt you to sign in, or update a license. Afterwards, I found I was able to open projects through Unity Hub again.