Hey there, kamran.
If that happens with all the devices you try the flash drive with (at least that's what I assume you're talking about), unfortunately, it really seems like it might have failed.
You could try downloading its manufacturers formatting tool (most SD card and flash drive manufacturers offer such tools for their devices), to see if it's able to recognize it and try to reformat it. Hopefully that fixes things up. Otherwise, I think it's RMA time if it's still under warranty.
Hope that helps. Please let me know how it goes.
Boogieman_WD