I am sorry to hear that you are facing an inconvenience. There are a few reasons why this message could appear. I have attached an article here that will walk you through the troubleshooting steps for the same.
If you are still facing the same issue after going through the steps mentioned in the article, I recommend reaching out to the Enrollment section of your school district who should be able to assist you in enrolling your child in the school district.
Remember to give Kudos to suggestions that help you! If a suggestion solves your issue, please select Accept As Solution on the post so others can see the solution, too!