I completely erased the old disk data and installed the 20.04 LTS version of Ubuntu but the Ubuntu software on the dock doesn't start. Then I ran in the terminal:
sudo apt install --reinstall ubuntu-software
It went fine. But still it doesn't open. Then I searched in dash for "software" and found two software center. One named Software and other Ubuntu Software. Software starts but Ubuntu Software doesn't start. In the dock there is Ubuntu Software which doesn't start.
Another thing, Running
sudo apt update says
All packages are up to date but in the Software it shows 2 updates needed. This is strange.
Why there are two software centers? One of them starts and the other doesn't. The one which starts shows pending updates but in terminal there is no pending updates.
Update: According to first answer I ran
snap-store form terminal and got this:
16:30:11:0219 Gtk Failed to load module "canberra-gtk-module" 16:30:11:0225 Gtk Failed to load module "canberra-gtk-module" 16:30:14:0571 Gs plugin appstream took 3.0 seconds to do setup 16:30:14:0580 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 16:30:14:0581 Gs disabled plugins: dpkg, dummy, fedora-langpacks, fedora-pkgdb-collections, repos 16:30:16:0144 Gs /etc/PackageKit/Vendor.conf file not found 16:30:17:0235 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)