Sometimes, when you plug in a camera (or other removable storage device) on a Windows computer and don't "safely remove" it, it won't show up when you plug it into a Mac. And vice-versa. Try plugging it into a Windows machine and then choosing "safely remove hardware" from the bottom right of the screen (system tray).
Then, when you plug it back into your Mac, it should work. Always eject/remove the hardware before physically disconnecting it.