Help with acquiring meeting attendee emails

[vhamilton123]

I work for a company that hosts several classes via Zoom meetings. We need to capture the attendees' emails, but we are having trouble. I have toggled the master setting of "Only authenticated meeting participants and webinar attendees can join meetings and webinars" to ON and manually toggle this same option to ON for each unique meeting. When I go into the reports and pull up the class attendee list, the entire email list is blank, apart from people who are directly added to the calendar invite. 

More context:

• Attendees sign up for the class via a third-party integration into our app -- they are prompted to add to their calendar
• People who are directly invited by our host account DO have their emails show up
• Waiting room is ON, no passcode

Does anyone know why this could be happening and how to fix it?