Hi Jeff
Could be because :
1. You are using an older version of the extension which is not compatible with Joomla 4. So if you are not using latest version, please update your site to latest version 4.3.0 of Events Booking
2. Or you are having an override base o code of old version of the extension. For this, submit a support ticket sending us super admin account of the site and link to the page which we can see the error so that we can check it
Regards,
Tuan
