FCPX 10.2.3 won't see external hard drives.
I just installed FCPX 10.2.3 on my 5k iMac. I formatted two usb external drives to OSX but Final Cut doesn't see them. One of the drives is empty!
iMac (Retina 5K, 27-inch, Late 2014), OS X El Capitan (10.11.5)