The Waiting Room is part of the Studio plan and the free trial. It keeps your Session private: once your first Guest is in, anyone else who arrives waits until you let them in.
If you'd rather let everyone straight in, turn on Auto Admit in the Waiting Room panel. Use it for classes or group Sessions where you're expecting everyone and don't want to admit people one by one.
Basic has no Waiting Room, because only one Guest can be in your Studio at a time. Instead, Basic has Knock to Enter: when someone arrives, they knock and you're notified, and you let them in when you're ready.
Basic and Studio both have Do Not Disturb, separate from the Waiting Room, for when you don't want to be interrupted.
If someone says they're waiting and you can't see them, check they're using your Studio link and not a page that links to it. See Invite people to your Studio.