Has the host joined the meeting? And as an authenticated user?
For testing sake, I would at least have the host start the meeting from the Webex Meetnigs client, then the attendees join via teams. That would rule out any issue for the attendees. If they still cannot join, check the settings for the meeting.
Also, if the host has locked the meeting, attendees will wait in the lobby until the host permits them in the room.
