Software Updater Update button Not Working

[mahesh]

I have a System76 Wild Dog running Ubuntu 18.04. I would like to update the OS to Ubuntu 20.04. Consistent with most instructions I've read about how to do this upgrade, I open the Software Updater app, which tells me if any of my apps or system need updates. I've installed all of the available updates for my system. The Software Updater informs me that all my software is up to date BUT that I am running 18.04 and 20.04.6 is available. It offers 2 buttons: "Update" and "OK." When I click on the "Update" button, nothing happens.

Is there some reason this app won't let me update my OS? I thought maybe I didn't have enough space on my computer, but I supposedly have 167 GB available, which should be plenty. I also have lots of memory on my computer (64GB).