Hi,
Sorry for the issues you are having. I can help resolve them with you.
Are you talking about the License Key or the Eventbrite API key
The License Key should be on this page:
Events > Settings > License Tab
The Eventbrite API key is in your user profile:
Users > Your Profile
Is either one showing?
If not can you please follow our testing for conflicts guide to see if that finds a solution:
https://theeventscalendar.com/support/documentation/testing-for-conflicts/
Let me know what you find out and we can go from there.
Thanks