It is important to note that all meetings are associated with a project, even if there's no project content or questions. You will have a project URL that will differ from your meeting URL.
Your project URL can be found on your project when you click View Live Site.
Each Meeting URL is unique. You'll find it in the dropdown menu on the meeting in the Meetings & Offline tab. (G666)
In order for your list of meeting attendees to populate, you'll need to share the meeting URL. Otherwise, attendees will only count towards your project views.
Use the meeting URL to publicize your meeting on your websites, social media posts, flyers, mailers, ect. in order to count those who join your virtual meeting as attendees. If your meeting is still upcoming, the green Attending button to the right of your meeting will note the number of attendees expected. You'll find participant info for attendees (and any RSVP's) in this list.
Once your meeting date has passed, the button will read Participated and notes the number of Participants.
Related articles:
How to create a new meeting or event
Signing participants into a meeting
How to collect questions for the meeting presenter
Entering paper survey responses
How to add an event to your project page