Further investigation notes: After extensive testing, it looks like you cannot execute a PXE orchestration if the server IP or MAC address are a duplicate of any other PXE request (in at least an "Environment Setup" status).
I ran into the same issue last Friday. Everything seemed to be okay, but I kept getting the error you referenced. What I found was that I had an existing request for the same MAC address in the "PXE Boot Requests" tab under Physical/{location}. I c...