I have a ubuntu machine, I had facing wifi connection(disconnection more often)
, then I forgot the network connection and tried to connect again. BUT

When I try to connect wifi from wifi interface in setting, after clicking on wifi network(wifi name), wifi interface disappears and reappears within 2 second, it does not show a window to enter password.

Then I tried to connect using terminal, it returns
Error: failed to add/activate new connection: Message recipient disconnected from message bus without replying.

As my laptop is out of connection and there is no Ethernet, I can’t attach any picture of it.
I did try to connect using both terminal and wifi gui, but can’t connect.