我在 Ubuntu 上使用 ProtonVPN 时遇到了这个问题，几天前它运行良好。我也尝试过多次重新安装它，但似乎没有任何效果。如果有人之前遇到过这种情况，请看以下输出：
Traceback (most recent call last):
File "/usr/bin/protonvpn-app", line 33, in <module>
sys.exit(load_entry_point('proton-vpn-gtk-app==4.2.0', 'console_scripts', 'protonvpn-app')())
File "/usr/lib/python3/dist-packages/proton/vpn/app/gtk/__main__.py", line 34, in main
controller = Controller.get(executor)
File "/usr/lib/python3/dist-packages/proton/vpn/app/gtk/controller.py", line 56, in get
executor.submit(controller.initialize_vpn_connector).result()
File "/usr/lib/python3.10/concurrent/futures/_base.py", line 458, in result
return self.__get_result()
File "/usr/lib/python3.10/concurrent/futures/_base.py", line 403, in __get_result
raise self._exception
File "/usr/lib/python3/dist-packages/proton/vpn/app/gtk/controller.py", line 89, in initialize_vpn_connector
self._connector = await self._api.get_vpn_connector()
File "/usr/lib/python3/dist-packages/proton/vpn/core/api.py", line 54, in get_vpn_connector
vpn_connector = await VPNConnector.get_instance(settings)
File "/usr/lib/python3/dist-packages/proton/vpn/connection/vpnconnector.py", line 66, in get_instance
await cls._instance.initialize_state(initial_state)
File "/usr/lib/python3/dist-packages/proton/vpn/connection/vpnconnector.py", line 149, in initialize_state
await self._update_state(state)
File "/usr/lib/python3/dist-packages/proton/vpn/connection/vpnconnector.py", line 250, in _update_state
new_event = await state_tasks
File "/usr/lib/python3/dist-packages/proton/vpn/connection/states.py", line 176, in run_tasks
await self.context.kill_switch.disable()
File "/usr/lib/python3/dist-packages/proton/vpn/killswitch/backend/linux/networkmanager/nmkillswitch.py", line 77, in disable
await self._ks_handler.remove_full_killswitch_connection()
File "/usr/lib/python3/dist-packages/proton/vpn/killswitch/backend/linux/networkmanager/killswitch_connection_handler.py", line 202, in remove_full_killswitch_connection
await self._remove_connection(_get_connection_id(permanent=False))
File "/usr/lib/python3/dist-packages/proton/vpn/killswitch/backend/linux/networkmanager/killswitch_connection_handler.py", line 228, in _remove_connection
await _wrap_future(self.nm_client.remove_connection_async(connection))
File "/usr/lib/python3/dist-packages/proton/vpn/killswitch/backend/linux/networkmanager/nmclient.py", line 230, in remove_connection_async
self._run_on_glib_loop_thread(_remove_connection_async).result()
File "/usr/lib/python3.10/concurrent/futures/_base.py", line 458, in result
return self.__get_result()
File "/usr/lib/python3.10/concurrent/futures/_base.py", line 403, in __get_result
raise self._exception
File "/usr/lib/python3/dist-packages/proton/vpn/killswitch/backend/linux/networkmanager/nmclient.py", line 118, in wrapper
future.set_result(function(*args, **kwargs))
File "/usr/lib/python3/dist-packages/proton/vpn/killswitch/backend/linux/networkmanager/nmclient.py", line 217, in _remove_connection_async
handler_id = device.connect("state-changed", _on_interface_state_changed)
AttributeError: 'NoneType' object has no attribute 'connect'```