One of my new Afci protected circuits trips immediately.

Hey wise sparkys and everyone else, I'm having a hard time trouble shooting a trip on an afci breaker-ed circuit. I ran 6 new circuits from a sub panel for a tiny house (all on afci breakers, 5 of them work fine). The one that trips will trip even with the hot wire disconnected from the breaker. What does this mean? Thanks in advance. Schneider home line panel & plug on neutral breakers if that helps.