disabled passcode but it still locks them out

I am making webinar content for a non-profit advocacy purpose in my county. I sent an invitation to judges, police, administrators and others --- only to find some people reporting back that after registering, they were told to give a passcode ---- but I had disabled the passcode.

All I can find in tutorials is to tell them to uninstall and reinstall Zoom. That's not an acceptable solution in this case.

I disabled it in Account Management, Settings, Webinars, Security. Also in each scheduled event.
Ruth J