Hi Smithy50,
Another point.
When the conect software is running press F6 the screen should change to machine mode.
If it asks for a password the press ALT P and enter conectl.
Click on MACHINE the click Machine Control.
If the serial port is correct then ON will appear if not then an error message will appear.

The options file in DOSbox needs the following in the serial port dialogue.

serial1=directserial realport:com1
Note: put the com number you wish to use mine was com1 only change the data after the : e.g. :com 2, :com3

My machine (lathe) beeps when the power is switched on and I believe it also sends a signal to the PC.

USB to serial ports are notorious for requiring the right driver version some will only work with older drivers.

I made a loopback connector and used a terminal programme to make sure it was working OK.

Hope this helps.