ubuntu 18.04 software-properties-gtk failing when I try to open the software&update it doesn't open and when I tried to sudo software-properties-gtk

it return this error

ERROR:dbus.proxies:Introspect error on :1.136:/: 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 173, in __init__

    self.backend.Reload();

  File "/usr/lib/python3/dist-packages/dbus/proxies.py", line 70, in __call__

    return self._proxy_method(*args, **keywords)

  File "/usr/lib/python3/dist-packages/dbus/proxies.py", line 145, in __call__

    **keywords)

  File "/usr/lib/python3/dist-packages/dbus/connection.py", line 651, in call_blocking

    message, timeout)

dbus.exceptions.DBusException: org.freedesktop.DBus.Error.ServiceUnknown: The name :1.136 was not provided by any .service files

I tried to reinstall software-properties-gtk but it didn't work
I also tried to reinstall python-six packages as recommended by other blogs but also didn't solve my issue.