If you are using a MSC MillMax kit this is the wrong interface setting. It is looking for different hardware than you have.
Open MillMax and click on Carbide Endmill button.
Click on red flashing Initialize button.
Press CTRL and A buttons on your keyboard at the same time.
Click on MillMax Preferences button.
Select SIM5 (MS 485B39) from dropdown menu.
Click OK
Restart MillMax.