I’ve gone ate by step to try and fix the issue, but I still get a rejection.
https://ttlc.intuit.com/community/rejections/help/rejection-code-ind-516-if-the-primary-taxpayer-is-claimed-as-an-exemption-in-the-return-then-the/01/26807
If your son's return is being rejected because he has already been claimed already then he cannot claim himself ... return to the MY INFO section and unclick this box ...