You would need to reach out to your school district and report this issue since this could be error with their firewall setup. You can check out the FAQs related to the enrollment process here.
I am getting the same error. I login with my username / password and then the site directs me to sign via a google account. When I choose my google account, it gives me the error you describe above. Were you able to solve the issue? If so, can you post how you did so? thanks!
The PowerSchool Community is a great resource if you have any changes to be made while completing fields within the enrollment form. Each district, however, has a different registration process and can provide the best steps to move forward when enrolling students.
Since access to the SSO link is managed by your district, you would need to reach out to your specific district and ask them to provide you the access. You can check out the FAQs related to the enrollment process here.