When you connect the board via USB, do you see any LED lights on the board? Could you please share a photo of your setup and also let me know what battery you are using to power the board?
Please be careful not to connect the board via USB only when the motors are connected as this could damage the board.
If you purchased the 2 axis gimbal controller board from us, then you will need to use the open source firmware/GUI which can be downloaded here
Although the board comes with firmware, it will be best if you try to upload the latest version again, for detail on how to upload the firmware with arduino please see the brushless gimbal (open source) help post
Hope that helps