I think this thread should be marked "unresolved."
I am still having this issue, as are others -or so it would seem.
I am running the most recent version of LibreElec on Raspberry Pi 3.
My wifi connection was working properly. Two days I logged on and libreelec could not connect to my wifi network.
The kodi/settings/libreelec/connections section shows "failure" for my default wifi connection.
When I try to manually reconnect I get the "network error / invalid arguments" popup immediately.
This is likely not a "password character length" issue as some have suggested. In fact, I get the error and never even get to the password entry field.
So, thinking it might be a config file or a cached file settings issue I created a new wifi name & password on my router and tried to connect to it. Again I get the immediate "network error / invalid arguments" popup without ever getting the chance to enter a password.
Net, I created an unsecured connection on my router and was able to connect to it through kodi/settings/libreelec/connections.
So... that was good, except that I didn't want to leave an unsecured connection open.
So I rebooted my raspberry pi device and immediately I had no connection on boot up and the same network error / invalid arguments popup.
since I can't get to a command prompt except through ssh, I don't know how to give more specific debug info, but will be happy to if directed.
Someone on another thread suggested a dbus issue?