This was fully expected, but much like the 1st generation Fire TV, I’ve confirmed that the new Fire TV running the latest Fire OS at version 5.0.2.1 only supports FAT32 drives. I tested NTFS and exFAT for both USB drives and microSD drives and neither one was mounted by the operating system. When inserting a non-FAT32 microSD card, the above message is displayed prompting you to format the card. Connecting a USB drive of any format, be it FAT32 or other, will not display any indication that the card was connected. It’s as if USB drive support is a hidden feature. When you connect a FAT32 USB drive, the drive will be mounted and accessible at /storage/usbotg. Connecting any other type of USB drive does not prompt you to format the drive. It simply does not get mounted and is inaccessible.