Hey there, koolx.
Do you get any specific error when you try to access it? Do you need data from it or you just want to make it work?
You should give it a go with a different computer/device as well, to see if the same thing happens. If you don't need to recover any data, you could try reformatting it or try that with its manufacturer's formatting tool (most SD card and flash drive manufacturers offer such tools for their devices), to see if that fixes things up.
Hope that helps.
Boogieman_WD