Hello,
first of all i do not know why you opened the drive since it voids the warranty.
furthermore you can refresh the drives of the drive manually with the system to see if that makes it work again
http://kb.sandisk.com/app/answers/detail/a_id/10/kw/usb%20not%20detected
if that does not help then you can test the flash drive on another pc, if there its also not detected then the drive seems to be defective and needs to be replaced
