please excuse the late reply. The error is only displayed because the debug of Librespot is called through a command without passing parameters here. This is because there is unfortunately no command for (this version of) Librespot that only displays the help. However, this does not affect the correct functioning of Spotify Connect. The name parameter is always automatically set with the name of the player (default „max2play“) – depending on what is set in Settings/Reboot.
Spotify Connect should run without any additional parameters in the command line options. Please make sure that you have installed your sound card correctly and that the audio output is set accordingly in the plugin.