Panelists not receiving zoom email notification

Can someone explain to me why on Tue this week when I added Panelists to my Webinar they all received Zoom email notifications of their specific link to enter webinar for practice session, yet on Wed when I added them to another webinar they checked box was not visible and the comments about sending email to Panelists was no longer visible.  Therefore the 2nd webinar, no-one received the Zoom email giving them access to the webinar early to practice?