you could try reformatting it but that will cause you to loose everything on it. More than likely it at the end of life. i had 2 usb boot drives go in a server in the space of a week, you really cant trust them. they only have a certain amount of R/W before they die.
I have people coming to me pretty much every day with USB drive issues, i always recommend to use cloud storage as its far more safe. you get 15GB of storage with a gmail account. its worth just making a fake account for the 15GB storage alone, plus u dont have to rely on bringing out a USB stick which can be easily lost and you can access the cloud storage on pretty much any device with internet access.