Can’t access USB flash drive anymore [duplicate]

Looking at the Chipgenius Dump, it is a Phison Controller.

You can try the following steps one by one and check if any of them helps:

  1. Download Rufus or Bootice and try formatting your USB drive in Windows.
  2. If above step does not help, connect the USB Drive to Linux Operating System and check if you can access the files. If you can, copy your files and format the drive in Linux using Gparted or Disk Utility.

If the above two don't help, then try this: download Phison Mass Production tools for your USB Drive from http://flashboot.ru/files/phison/ and try formatting your USB Drive. You will have to try with each tool until you succeed. This tool will try to reprogram your USB Drive's Microcontroller and format it again. NOTE - This will delete all the files in your USB Drive.

Check this link for a detailed guide on how to do this (in this guide the MPtool is being used to repair a fake USB Drive): http://agnipulse.com/2010/04/how-i-fixed-a-fake-64gb-usb-drive/

Look at these answers for details on Mass Production tools: Flipping the Removable Media bit -- alternatives to BootIt? and How to format/repair a write-protected USB drive with I/O errors?

Hope this helps. Let me know how it goes.