There are different reason why your computer will not recognize your device once you connect it and they are as follows:
1. Device is connected to the computer with power OFF.
If this happens unplug the device and turn it ON then plug it back in.
2. The USB cable that you are using is defective.
Replace the USB cable with a new USB cable. If you have a different USB cable that has been tested as working then you may try that before buying a new one.
3. The USB is not enabled on your computer BIOS.
You must enable the USB on your computer. Please contact computer manufacturer support if you are not familiar as to how to access the computer BIOS and enable USB.
4. The USB that you are using is not supported.
5. PC device jam.
Just simply reboot the PC. If that does not work then completely turn off the computer and wait for 2 minutes before turning it back on.