Check the USB connection at both the printer and PC end.
Close other software that may be trying to access the printer, like any other slicer software, including Makertech Cura and the Arduino IDE also.
Check PC/MAC firewalls and
antivirus software that might be blocking the connection.
Make sure that you have the drivers installed:
When installing the driver make sure you are running as administrator and can make the necessary changes to your PC.
This driver is also available from the chip manufacturer here:
If the above does not work:
1. Unplug the end stops from the board and try connecting again.
2. Unplug all connections to the board, including the stepper drivers and try the connection again.
3. Try resetting (the red button on the centre of the board) with everything removed from the board whilst connected via USB.