Hi dominantmusic,
Can you confirm for me that you are running the latest version of each plugin? That would be The Events Calendar 3.5.1, Eventbrite Tickets 3.5, and Events Calendar PRO 3.5.1. Also, make sure they are all activated on your Plugins page. If they are still not showing under Events –> Settings –> License Keys, please send me a screenshot of that whole screen so I can troubleshoot further. I recommend that you make your response Private so that no one else can see your license key.
Best,
Leah