Hi Lori,
Thanks for reaching out!
First, could you try updating to the current versions of the plugins (The Events Calendar: 4.5.12.2, Event Tickets Plus: 4.5.4) and see if you can see the attendees? If you don’t see prompts to update in the Plugins section of your Dashboard, you can do so manually by following these instructions.
If not, the next step would be to test for conflicts with your theme and other plugins. If you prefer to do this in a testing environment, WP Staging will let you create a quick copy of your live site that you can use for testing.
Let me know how it goes!
Thanks,
Jennifer