I am going to answer my own question.
Recently, I unticked the setting for NC to start with Windows, because I was working on a script that changes a ton of files when saving and was having problems with conflicts, when saving frequently.
When I was done, I ticked the setting again and thought nothing of it. Next time I booted up my OS, the NC client wouldn’t start. I went back to the settings and sure enough, the box was ticked.
I unticked the box, rebooted the OS, ticked the box, rebooted the system, but nothing changed. I perused the Internet for a solution, but it seems my google-fu (actually ddg-fu) is not what it used to be; I turned up empty.
Starting the client manually with the crank handle works and the client does what the client does and has a poker face about the issue of not respecting the ‘start client with windows’ setting.