Start with GOOD cables and follow the instructions for a hardware flow control (handshaking)
Baud 2400
Parity none
Data Bits 8
Stop Bits 2 but could really be 1.
It seems to set up like any other machine would (this was my first) though I couldnt find any posts specific to feeing a Dyna DM 2400. There was a bunch of conflicting wiring diagrams in the manual/s though. Those didnt help. Dont give up on it if it comes to life.
Time to see it cut something under computer control.