It sounds like you are trying to get the Pololu Simple Motor Controller 18v17 to work on your system running Linux Mint. I am not familiar with Linux Mint, so it is difficult for me to say what the issue might be. Could you try using a different USB cable (one that you know is working) and a different USB port? Can you run dmesg in a terminal immediately after plugging in the motor controller to your computer and post the output results here?
in the meantime I tried it allso with Win 8.1 and Win 7. With the same result.
So I bought a new USB-cable and tests with both Windows versions had been succesfull.
With LinuxMint it should work too.
I think the first cable is only for charching and not for data transfer.
The 18V7-controller is a nice electronic part and easy to configure with your software.