You did not yet state what PC operating system… Windows, Linux, Mac? If using Windows, run the full CLI installer again… I would not use the npm method because it doesn’t update the windows drivers, and resolve the dependency issues (I think?), if needed.
I had issues with getting the Argon to recognize on Serial as well. I ended up applying the USB Serial driver using the Zadig utility as recommended by @ScruffR in this post… that recommendation was before RC27 so I’m not sure if the driver installation is more solid now. Again, if Windows, check your Device Manager and look for “Argon CDC” or equivalent with an exclamation.