Software & Updates not opening in Ubuntu 20.04 LTS

Software & Updates is not opening via any method, be it GUI or command line. On opening using click on icon nothing happens. If I execute sudo software-properties-gtk , the following error shows in the terminal:

ERROR:dbus.proxies:Introspect error on :1.118:/: dbus.exceptions.DBusException: org.freedesktop.DBus.Error.NoReply: Message recipient disconnected from message bus without replying
Traceback (most recent call last):
  File "/usr/bin/software-properties-gtk", line 100, in <module>
    app = SoftwarePropertiesGtk(datadir=options.data_dir, options=options, file=file)
  File "/usr/lib/python3/dist-packages/softwareproperties/gtk/SoftwarePropertiesGtk.py", line 222, in __init__
    self.backend.Reload();
  File "/usr/lib/python3/dist-packages/dbus/proxies.py", line 72, in __call__
    return self._proxy_method(*args, **keywords)
  File "/usr/lib/python3/dist-packages/dbus/proxies.py", line 141, in __call__
    return self._connection.call_blocking(self._named_service,
  File "/usr/lib/python3/dist-packages/dbus/connection.py", line 652, in call_blocking
    reply_message = self.send_message_with_reply_and_block(
dbus.exceptions.DBusException: org.freedesktop.DBus.Error.ServiceUnknown: The name :1.118 was not provided by any .service files

I have tried reinstalling software-properties-gtk but it did not help.

Edit 1 : I have not played with python installation on this machine. This just stopped working after I executed sudo apt update followed by sudo apt upgrade.

Edit 2 : I executed the solution proposed by N0rbert and here is what it show up in the terminal.

Traceback (most recent call last):
  File "/usr/bin/software-properties-gtk", line 100, in <module>
    app = SoftwarePropertiesGtk(datadir=options.data_dir, options=options, file=file)
  File "/usr/lib/python3/dist-packages/softwareproperties/gtk/SoftwarePropertiesGtk.py", line 222, in __init__
    self.backend.Reload();
  File "/usr/lib/python3/dist-packages/dbus/proxies.py", line 72, in __call__
    return self._proxy_method(*args, **keywords)
  File "/usr/lib/python3/dist-packages/dbus/proxies.py", line 141, in __call__
    return self._connection.call_blocking(self._named_service,
  File "/usr/lib/python3/dist-packages/dbus/connection.py", line 652, in call_blocking
    reply_message = self.send_message_with_reply_and_block(
dbus.exceptions.DBusException: org.freedesktop.DBus.Error.ServiceUnknown: The name :1.101 was not provided by any .service files

Edit 3 : Output of SYSTEMD_PAGER= systemctl status dbus* is :

● dbus.socket - D-Bus System Message Bus Socket
     Loaded: loaded (/lib/systemd/system/dbus.socket; static; vendor preset: enabled)
     Active: active (running) since Fri 2022-01-21 12:17:40 IST; 2h 24min ago
   Triggers: ● dbus.service
     Listen: /run/dbus/system_bus_socket (Stream)
      Tasks: 0 (limit: 9283)
     Memory: 0B
     CGroup: /system.slice/dbus.socket

Jan 21 12:17:40 vivobook systemd[1]: Listening on D-Bus System Message Bus …ket.

● dbus.service - D-Bus System Message Bus
     Loaded: loaded (/lib/systemd/system/dbus.service; static; vendor preset: enabled)
     Active: active (running) since Fri 2022-01-21 12:17:40 IST; 2h 24min ago
TriggeredBy: ● dbus.socket
       Docs: man:dbus-daemon(1)
   Main PID: 777 (dbus-daemon)
      Tasks: 1 (limit: 9283)
     Memory: 4.9M
     CGroup: /system.slice/dbus.service
             └─777 /usr/bin/dbus-daemon --system --address=systemd: --nofork --…

Jan 21 14:10:53 vivobook dbus-daemon[777]: [system] Activating via systemd:…ed")
Jan 21 14:10:53 vivobook dbus-daemon[777]: [system] Successfully activated …her'
Jan 21 14:17:44 vivobook dbus-daemon[777]: [system] Activating via systemd:…ed")
Jan 21 14:17:44 vivobook dbus-daemon[777]: [system] Successfully activated …her'
Jan 21 14:26:13 vivobook dbus-daemon[777]: [system] Activating via systemd:…ed")
Jan 21 14:26:13 vivobook dbus-daemon[777]: [system] Successfully activated …her'
Jan 21 14:27:18 vivobook dbus-daemon[777]: [system] Activating via systemd:…ed")
Jan 21 14:27:18 vivobook dbus-daemon[777]: [system] Successfully activated …her'
Jan 21 14:41:47 vivobook dbus-daemon[777]: [system] Activating via systemd:…ed")
Jan 21 14:41:47 vivobook dbus-daemon[777]: [system] Successfully activated …int'
Hint: Some lines were ellipsized, use -l to show in full.

I would recommend to reinstall all Dbus-related packages by

sudo apt update
sudo apt install --reinstall $(dpkg -l | grep ^ii | grep -i dbus | awk '{print $2}')

Then reboot and retry launching Software & Updates by plain software-properties-gtk command without sudo again.