Unable to use Software Center: All mirrors were tried; 404

I’m no longer able to use the Gnome Software Center in Fedora 34. Initially, when attempting to install anything, I would get the error:

All mirrors were tried; Last Error: Status Code: 404

Installing packages through the terminal with dnf is fine. I attempted to run pkcon refresh and that seems to have made things worse, because now attempting to install anything with Gnome Software gives this error instead:

For example, attempting to install Bottles:

Unable to install Bottles: Failed to find bottles;2021.7.14-1.fc34;noarch;updates