Hi, jjwpacker1-

Here is an article stating why your son may not have received an email: https://khanacademy.zendesk.com/hc/en-us/articles/202959854-Why-haven-t-my-students-received-their-invitation-emails-after-I-invited-them-to-join-my-class-

If your son already has a Khan Academy account linked to that email address, then the invitation will show up in his notification box instead of his email. Have him log into his account and then check his notifications for the class invitation.

He can also add you as a coach from his dashboard by following the steps in this article: https://khanacademy.zendesk.com/hc/en-us/articles/360030561952-How-do-I-add-a-teacher-for-myself-

Best of luck, and happy learning!