Hello Henry,
Thanks for choosing the Apple Support Communities. If we understand correctly, a new contact was added to an email distribution group but they are not showing up. We can understand why you'd reach out for a solution.
Try these troubleshooting steps:
Quit the Mail app on your iPad and restart the device to refresh it.
Go to www.iCloud.com from any computer and check to see if the new member is showing in the group.
If not, try entering the contact again.
Create and manage groups of contacts on iCloud.com - iCloud User Guide
If your iCloud Contacts, Calendars, or Reminders won’t sync
If the issue persists after trying these steps, please reply back to this thread and we'll do our best to help you!
Have a great day!