I decided to plug in an external hard drive into my QNAP and copy files to it. I did this with 2 hard drives and rotated them last month. This month I unplugged 1 of the drives and plugged the other in and the QNAP won't recognize it. This is happening with both drives. Neither is recognized by the QNAP but they worked fine before when I swapped them out. Any suggestion on what I could try? Is the USB port bad?