Hi Judy,
Thanks for getting in touch and explaining the issue. The most recent version of Eventbrite Tickets is 4.0, which is why you are getting an alert to update your version 3.12.1.
It looks like your Eventbrite Tickets license key was registered to your site at some point in the past, but is no longer properly connected. To correct, that, first go to your license keys page and find your Eventbrite Tickets license. Click the Disconnect Now link next to the site url (as described here). Then head back over to your WordPress site and drop the license key into the field underĀ Events –> Settings –> License Keys. Be sure to save that page so the key validates.
Once the key validates properly, your site will be able to receive updates. You will probably need to go to the WordPress Updates page and click the Check Again button (maybe even a few times), but then an update for the plugin will appear as an option.
If you have any trouble along the way, please take a screenshot and post it here so we can troubleshoot further. Thank you for your support!
Best,
Leah