Per https://gozwift.kustomer.help/en_us/-how-to-give-multiple-ride-ons-at-once-S1Wag0ybS7, the “multiple ride-on” feature is disabled in group rides.
I would love for this feature to be enabled in events like the Zwift Fondo series, or the Tour of New York, etc., as well as races (perhaps controlled by the race organizer). In most group rides, I end up finding a nice little peloton where we’re all at about the same level, and we’re pushing and working together. For me, this is the social aspect of Zwift at its best, and I would love to be able to encourage my peloton’s collaboration without having to find and click on every user. This is especially difficult as the line-up is reordering itself.