Hi - I've spent over two hours trying to figure out why Trello will not allow me to convert single board guests into multi board guests. I am admin and have a premium account. For reference, there are currently 9 multi board guests associated with my account and I need to add three more. If I remove an existing multi board user from the board then the single board users can access and essentially take the "empty seat." I thought premium offered unlimited multiboard guests though?