https://ttlc.intuit.com/community/taxes/discussion/what-is-reject-code-seic-f1040-506-02/00/657980#:~:text=2)...-,Rejection%20SEIC%2DF1040%2D506%2D02%3A%20On%20Schedule%20EIC,child%20on%20a%20different%20return.
That code comes up in a Google search that someone else claimed a dependent you are claiming.
@ron_bingham See this link for more information regarding the rejection code.