|The flash drive (or external drive, or memory card reader) must be plugged into a port it will actually work in.|
How to tell if the flash drive (or external drive, or memory card reader) is properly recognized as a hardware device, even if you can't access it's data.
Programs you can try to recover your data, if that's okay.
The most frequent reason people can no longer access the data on a USB flash drive, USB External drive, or a memory card on a computer
See Response 2: