Amending a 2022 Return for Dependent Status

I just filed my son's Federal return and inadvertently failed to indicate that he would be claimed as a dependent on my return.  His return was accepted.  When I just went to file my own Federal return, it was rejected because I claimed him as  a dependent and he did not indicate that he would be claimed by me.  I went to amend his return (since its been accepted) and I cannot see where it is that I can change his dependent status.  There is a Personal Info & Dependents section but it does not provide an option to update that item.  This is a big deal because I have education expenses and 529 plan earnings on my return.  Appreciate any assistance.  Thanks.