The Waiting Room

[Sultans7Secrets]

When I've created meetings in the past and included a waiting room, once I've started the meeting and let everyone in, I have been able to disable the waiting room and all of the latecomers can join bypassing the waiting room. Now that function appears to be grayed out during the meeting. I can't find anything in the settings to change it. How do I change that so I can disable the waiting room during a meeting after I no longer need it?