A RS232 break out box is invaluable for trouble shooting these type of problems, normally HW Handshake takes care of these alarms, DR pin is pin 6 on the 25D.
With a Break out box, you can see the actual level of the signal, which on most boxes is a red LED for low and Green for high.
It should be High.
There is also normally two ports on the 0, one on the MB and the other on the Operator Panel, check to see if there is CD1 socket.
If you need the RS232 manual on this, send me a email ad by PM.
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.