1. RS232 must be on Okuma. DNC function is optional. Check with OSP Data MAagement Card.
2. Look if there is DB-25 connector.
3. Serial cable diagram. Looking at the cable I think there are only 3 lines? Not enough for troubleshooting.
4. What are connectivity and troubleshooting tools on that microbox? Isn't it better to take just a computer with RS232 to check connectivity?