I downloaded the Gateway and Client Serial modules from the Download section of your web site.
Each of these downloads was a zip file.
When I extracted the zip files I got files with extension .jar (gateway module) or .jar.pack.gz (client module).
In the Ignition Gateway when I try to install the modules, it asks for me to point it at the .modl files, but there were no .modl files in the downloads.
What am I missing?