Ron,

See the message "Could not connect to /dev/cu.usbserial"

In the INDI control panel for the nStep you need to select the correct port or force set it
In a terminal window, do a
ls -ltr /dev/*usb*

You shoudl see something like
/dev/cu.usbmodemXXX
/dev/tty.usbmodemXXX

See the image of my control panel above, notice the row with the Ports on it

Copy the text of the file name (e.g. /dev/cu.usbmodem621) shown for the cu device and open your control panel, paste the device name into the right field of the Ports and do a 'Set'
Then on the Option tab of the control panel, do a Save
Then try your connect.

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