Software & Updates doesn't open in 20.04 LTS

I cannot open Software & Updates, either by going to Activities, and clicking on the Software & Updates icon, or trying to open it from the terminal with the command:

software-properties-gtk

I have also tried reinstalling:

sudo apt-get install --reinstall software-properties-gtk

After the re-installation, it either doesn't open, or, if it does, it just shows an empty white screen. What is the problem here?

I am running Ubuntu 20.04.

I've figured it out! Apparently, I needed to run the software-properties-gtk command with root privileges, like

sudo software-properties-gtk

And now everything works just fine. Also running `

sudo journalctl -f

and then launching the app worked well too.

I had the same problem and sudo software-properties-gtk did not solve it.

However, as suggested by this answer in Ask Ubuntu the following command solved it:

sudo apt-get update && sudo apt-get install --reinstall python3-six python3-certifi