When parents sign up for Girl Guides on the Girl Guide's registration system, the parent's email is sent to ePACT. From there, they will receive an invitation to complete the ePACT record for their child. There shouldn't be any intervention necessary on your end.
However, it's possible that either of the following situation have occurred:
1. A child was registered under an alternate email address and the parent hasn't checked the correct inbox.
2. The email may have been delivered to their spam/junk folder.
3. They might have just signed up that day, so they haven't been added to the system just yet.
4. Another parent/legal guardian registered the child under a different email and received the invitation.
If any of the above are of concern, feel free to point them in the direction of our support desk (help@epactnetwork.com) and we can help further.