I think you have to receive the link in the email coming from your ISD email, something like this:
"Please check your email account for an email titled “XXX ISD Registration” that will come from “PowerSchool Registration Support.” You will click the ‘Snapcode’ link in the email to access the Returning Student Registration site. Please complete the registration process prior to the first day of school (August XX). It is required for all returning students."
I'm having trouble receiving the email for one of my children to register. We got the link in the email for the other child.
Hope it helps.
I got a reply from Support, saying that we need to contact our child's school for registering. Apparently, there is long wait at the registration office. Our district has schools started this Wed Aug 9, 2023.