Hey Tom,
Thank you for reaching out to us!
We unfortunately don’t have the necessary experience to help you with this specific query.
A piece of advice I can give you, is to make sure that “tribe_events” is not excluded from search by default. If the event custom post type is being excluded, head over to “Relevanssi -> Exclusions and restrictions -> Respect exclude_from_search for custom post types” and uncheck the box.
Also, I would recommend you posting this same question to the Relevanssi folks to see if they have any insight on how to setup this custom query.
I wish you the best of luck with your searching! Let me know if you need anything else in the mean time and I’ll be happy to assist!
Regards,
Patricia