Make sure your usb cable works fine.
Try with different usb ports of computer.
Uninstall usb drivers from device manager .
For that right click on my computer icon then click on property then hardware->device manager.
Then you can see all driver list uninstall all usb drivers 1 by 1 then it automatic install all usb drivers.
If you have windows then you need to change in registry settings.
for that
1. Click on the start menu.
2. If this is a Vista machine in the search box type in “regedit” without the quotation marks.
3. Maximize the HKLM and then go ahead and browse until you reach the key listed below.
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E965-E325-11­CE-BFC1-08002BE10318}
4. In the right panel you’ll see something along the lines of “UpperFilter” and “LowerFilter” you want to click on each “filter” key and hit delete. Click yes when it asks to confirm if you wish to delete the key.
5. Restart Windows.

Then check
Let me know if you need further assistance.
Thanks for using FixYa.