RSVP Block won’t load – error msg

RSVP block will insert into pages, but not into regular events (events are being handled by a church plugin, not by events calendar)

Error “This block has encountered an error and cannot be previewed”

Theme creator and church plugin are by same dev, who is looking into it has asked “Does the maker of the plugin/block have any idea why this might be happening?”

If someone does have an idea or pointer, please do comment