[ubuntu] Cannot launch Ubuntu Software Center after installing 20.04

I just installed 20.04. Every time I click on the Ubuntu Software Center icon in the left-hand dock, the tab shows up in the top tray with the waiting animation, then disappears.

I finally figured out that the command is snap-store (not software-center), and in a terminal I get this:

01:41:16:0845 Gtk Failed to load module "canberra-gtk-module"
01:41:16:0848 Gtk Failed to load module "canberra-gtk-module"
01:41:16:0922 Gs enabled plugins: desktop-categories, fwupd, os-release, packagekit, packagekit-local, packagekit-offline, packagekit-proxy, packagekit-refine-repos, packagekit-refresh, packagekit-upgrade, packagekit-url-to-app, appstream, desktop-menu-path, hardcoded-blacklist, hardcoded-popular, modalias, odrs, packagekit-refine, rewrite-resource, packagekit-history, provenance, snap, systemd-updates, generic-updates, provenance-license, icons, key-colors, key-colors-metadata
01:41:16:0922 Gs disabled plugins: dpkg, dummy, fedora-langpacks, fedora-pkgdb-collections, repos
01:41:17:0090 Gs /etc/PackageKit/Vendor.conf file not found
01:41:17:0618 Gtk Could not load a pixbuf from icon theme.
This may indicate that pixbuf loaders or the mime database could not be found.
**
Gtk:ERROR:../gtk/gtkiconhelper.c:494:ensure_surface_for_gicon: assertion failed (error == NULL): Failed to load /snap/snap-store/433/data-dir/icons/Yaru/16x16/status/image-missing.png: Unrecognized image file format (gdk-pixbuf-error-quark, 3)
Bail out! Gtk:ERROR:../gtk/gtkiconhelper.c:494:ensure_surface_for_gicon: assertion failed (error == NULL): Failed to load /snap/snap-store/433/data-dir/icons/Yaru/16x16/status/image-missing.png: Unrecognized image file format (gdk-pixbuf-error-quark, 3)
Aborted (core dumped)


Any solutions?