Can't Access External Storage?
If you're having trouble using external storage with your Amazon Fire TV device, first make sure you're
using a supported storage device. For Amazon Fire TV (1st Generation) you can use a compatible USB
flash drive for external storage. To learn more, go to USB Storage for Amazon Fire TV.
External storage options are not available for Fire TV Stick.
If your storage device is compatible, try safely removing and then re-attaching it to your Amazon Fire TV:
Go to Settings > System and select your storage device.
Select Eject.
Wait for the on-screen confirmation before safely removing the device.
Re-attach your storage device.