A few reasons for the issue that you are encountering while trying to submit the registration form could be the required field that is missing information or a field with information entered in an invalid format. You could check those fields before you try to submit your form through the following steps.
I would recommend filling out the form using Google Chrome or Mozilla Firefox browsers as our Enrollment forms work with these browsers.
Additionally, I recommend clearing the cache, browser history, and cookies of your internet browser. I have attached an article here that should help walk you through the process of clearing the cache, browser history, and cookies of your internet browser.
I am providing a document that provides further instruction on how to complete the contact priorities. You can review the document here.
If you continue facing the issue even after trying all the troubleshooting methods, I recommend reaching out and submitting a ticket to the PowerSchool Enrollment Family Support team, who would be glad to assist you with any Enrollment issue.