Re: sd card blank unsupported files
Welcome to Android Central! What phone do you have? Was the card working up until recently? Any recent system updates? I have read of occasional issues with the SD card if it is kept in during a system update. Do you recall removing the card without unmounting it first in Settings>Storage? This can cause problems as well, much like pulling the plug on your computer while it's in the middle of writing to the hard drive.
Unmount the card, remove it, and insert it into your computer's SD reader. Does the computer detect any files?