Can't turn off Waiting Room

Welcome to the Zoom Community, @normangoldfarb.

Did you have a Passcode associated with your Personal Meeting?  If not, the Waiting Room menu item in the in-Meeting security menu will be greyed out, as you are required to have at least one security measure in place at all times.

With the exception of Enterprise, API, Business (with more than 100 licenses), or Education accounts, this is a requirement:

... all meetings to be secured with [at least] one of the following security options: a passcode, Waiting Room, or Only authenticated users can join meetings. These options provide additional protection and privacy for your meetings and help prevent uninvited guests from joining.

Text taken from the introduction of this Zoom Support article:

https://support.zoom.us/hc/en-us/articles/360059665892-Requiring-meetings-to-have-one-security-option 

Enable either Passcode or Authentication in order for the Waiting Room to be "optional".