1] A simple restart of the Windows computer can sometimes solve this problem. Unplug your USB, restart you computer and plug in and see if it works now. If it does not, shut down your computer, wait for a few minutes and then start your computer again.
2] To avoid a possible conflict between two connected USB Devices, disconnect your other USB’s, connect this one and see if it helps.
3] Run devmgmt.msc to open Device Manager. Under Action tab, select Scan for hardware changes and see if it helps.
USB Device Not Recognized in Windows 8
3] Check if you need to update your drivers. Open Control Panel > Printers and devices. Check if you can see any entry for Unidentified USB device or Unknown Device. Open its Properties and update its driver, if an update is found to be available.
Unidentified USB device4] From the Device Manager, under USB Root Hub Properties, uncheck Allow the computer to turn off this device to save power. See if this helps. If not check it back again.
Allow the computer to turn off this device
5] Run the Hardware and Device Troubleshooter or the Windows USB Troubleshooter and check if it helps. The automated tools check the hardware or USB connected to the computer for any known issues and fix them automatically.
6] If you are using Windows 8, Windows 8.1, Windows Server 2012 R2 or Windows Server 2012, there is a specific issue that affected this version of Windows. This could happen, if your USB port gets disabled after you safely remove the device from the port. Download and request a hotfix from KB2830154 if you face this issue.
7] If its your USB 3.0 device that are not being recognized, see this post on USB 3.0 External Hard Drive not recognized in Windows. Also see this post USB Devices not working in Windows.
Hope something helps.
Have more tips on this? Let us know them via comments section below.
Ethan Stark
http://cloudappsportal.com/